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Window air conditioners are very simple appliances. They operate on the exact same principles as a refrigerator, freezer, or dehumidifier.

Please look for information on how window air conditioners work in these areas:

All residential window air conditioners have a cooling system made up of four primary components, a compressor, an evaporator, a metering device, and a condenser. Air conditioner cooling systems are better understood if you think of them as devices that remove warmth from the air rather than cooling the air.

Blower fan
When the unit is running, the circulating fan and compressor are running simultaneously. The fan motor has two fan blades attached to it on either end. The fan blade on the inside part of the unit continually draws room air over the evaporator coils, which are cold. The fan blade on the outside part of the unit continually draws fresh outside air over the condenser coils, which are warm. Because the evaporator coils are cold, they cause moisture in the room to collect on them, much like a cup of ice water on a warm, humid day. When the amount of moisture increases, it begins to drip down off of the coils into the bottom pan of the air conditioner.

Thermostat control
The thermostat on a window air conditioner works by sensing the air temperature entering the air conditioner. As the air entering the unit reaches the set temperature it will cause the compressor to turn off. The blower may continue to run depending on the selection chosen on the control panel. Digital thermostats work on a similar principle but display a more precise temperature.

Selector switches
The air conditioner selector switches allow the user to choose the fan speed. The compressor always runs at the same speed regardless of the settings. If low cool is chosen, for example, the fan runs at a slower speed but the compressor still offers the same cooling capacity. There are other switches to control louver operation and other features on some units.


It doesn't turn on at all
Check to see if there is power getting to the air conditioner. If it is a 110-volt unit, plug a lamp or other device into the same outlet the air conditioner is plugged into. If there's no power, check the fuses or circuit breakers. If there's still no power, you will need to contact a qualified electrician to restore power to the outlet.

If there is power to the appliance but it is still completely dead there may be a problem in one or more of the following areas:

  • Wiring (Inspect for any broken or burnt wiring)
  • Thermostat
  • Compressor
  • Overload and/or relay
  • Selector switch
  • Control board

Work on these areas of an appliance may require help from an appliance repair person or other qualified technician.

The fan runs but there's no cold air?
Is the air conditioner completely dead? See section 1. Is the thermostat knob turned to the proper setting? Is the compressor motor running? The compressor is a football-sized case with no apparent moving parts. It is located inside the air conditioner at the center. Is it humming or making any kind of continuous noise or causing the lights to dim? If it is making a continuous noise, and your air conditioner is still not cooling at all, there may be a serious problem with one or more of these areas:

  • Compressor
  • Condenser
  • Evaporator

These items are not user serviceable. You will need to contact a qualified appliance repair technician to repair these components.

If the compressor is not running but you do have power to the air conditioner there may be a problem in one or more of these areas:

  • Compressor
  • Overload and/or relay
  • Thermostat (Open thermostat)
  • Burnt wiring
  • Bad selector switch
  • Capacitor

The air is cool but doesn't seem cold enough
If the air doesn't seem cool enough it is necessary to use a thermometer to check the difference in temperature between the air going into the unit and the air being blown into the room. Ideally, the temperature difference should be more than 15 degrees. For example, if the temperature going into the air conditioner is 80 degrees, the temperature coming out of the unit should be at least 65 degrees or less. If the difference is 15 degrees or more there is probably no cause for concern. If the temperature difference is less than 15 degrees you should check the following:

  • Air damper
    Check to make sure the air damper is closed. If it's open, it will bring in outside air and reduce the efficiency of the unit.
  • Back cover
    During the winter season many people cover their air conditioners to protect the unit from the weather. In the spring or summer they will sometimes forget to remove the cover. If your unit has a cover on the outside portion of the air conditioner remove the cover first.
  • Condensing coils
    The condensing coils will always be on the "warm" side of the air conditioner. That is, on the side that faces outside of the room to be cooled. Air is drawn into the back of the air conditioner on the sides through vent slots and is blown directly out through the condenser coils. If the coils get clogged with lint, dust and dirt the cooling system cannot provide the cooling necessary. To clean the coils it will be necessary to remove the entire cover of the air conditioner or pull it out of the wall to gain access to the coils. They can be cleaned by blowing compressed air at them or by using a soft bristle brush to wipe the dirt off. It is important to also clean any dirt or lint build-up in the bottom of the air conditioner so the condensate water will be picked up by the condensing fan slinger properly.

The unit never turns off
This is normal on some models when fan is set to run constantly.

If the unit is supposed to turn off and it doesn't, it will be necessary to check several things.

  • First, is the unit cooling properly? See the section entitled "The air is cool but doesn't seem cold enough."
  • Next, is the temperature of the room adequately cool? If the room temperature is cold enough try setting the thermostat to a higher temperature. If the unit then seems to work properly leave the thermostat set to the higher temperature.
  • If the unit is cooling properly when it is turned on and the room is not cool enough the problem is probably that the unit is trying to cool an area that is too large for its capacity. Use the following chart to find the appropriate size air conditioner to use:

    100 to 150 square feet = 5,000
    150 to 250 square feet = 6,000
    250 to 300 square feet = 7,000
    300 to 350 square feet = 8,000
    350 to 400 square feet = 9,000
    400 to 450 square feet = 10,000
    450 to 550 square feet = 12,000
    550 to 700 square feet = 14,000
    700 to 1000 square feet = 18,000

    If the room is heavily shaded, reduce needed capacity by 10%

    If the room receives a lot of direct sun, increase needed capacity by 10%

    Add 600 Btu/Hr for each person in the room if there are more than two people

    If the unit is for a kitchen, increase the capacity by 4,000-6,000 Btu/Hr.

    If the room size is too big for the air conditioner you have two possible choices. Either decrease the room size by shutting some doors or partitioning off an area of the room. Or, increase the BTU of the air conditioner for that room by installing a different air conditioner with a higher BTU rating.

There is water sloshing around inside
All window air conditioners will remove moisture from the air if there is any. Most window air conditioners collect this moisture in the bottom pan of the air conditioner and attempt to evaporate the moisture. The evaporation process works as follows: First, the water drips down off of the cold evaporator coils on the front of the unit. Then the water collects in the bottom of the air conditioner base, the "pan." If the air conditioner is installed properly it will be tilted slightly back.

The water then collects near the back of the unit. On some units, the fan blade used to cool the rear condensing coils will have a rim on the outside of the fins of the blade. This rim, or "slinger," will come close to touching the inside of the air conditioner pan when the fan is spinning. As the water collects in the pan and reaches the depth necessary for the fan ring to touch it, the ring will lift some of the water up and the fan will blow it at the condensing coils. Because the coils are warm, they will evaporate the moisture to the outside.

While this is happening it is normal to hear water splashing and sloshing around. As long as there is no water leaking inside the room that is being cooled there is no cause for concern.

Never drill into the bottom of and air conditioning unit to "let the water out."

The unit tries to start for a few seconds and then quits
Every air conditioner has a motor called a compressor. The compressor provides the cooling capacity for the air conditioner. If the compressor or its electrical controls are defective the compressor may try to start, fail, and create an electrical overload. If the unit does create an overload, every compressor circuit is also equipped with an overload safety switch. The safety switch is designed to protect the compressor from burning out. The safety switch will cut the power to the compressor for a certain length of time and then reset itself. When it resets it will allow the electricity to flow to the compressor once again. If the compressor then starts, the unit should function normally. If the compressor doesn't start when the overload resets, the overload will again cut the electricity to the compressor. This cycle will continue indefinitely. (Always allow three to five minutes before restarting the compressor.) If this situation is occurring, unplug the air conditioner and get help from a qualified repair technician. This problem is often fatal to the air conditioner because the cost of repair often exceeds the price of a new air conditioner.

A motor is running but there is no air blowing
Every air conditioner is equipped with at least two motors, the compressor and the fan motor. It is possible for the fan motor to be defective and the compressor to be running. If this is the case the unit will appear to be running and may even sound "normal" but no air is blowing out the front or back of the unit. If, after removing the cover of the unit you discover the fan blade is very stiff and difficult to rotate, the fan motor should be replaced. If the fan blade turns freely the circuit powering the fan motor will require electrical troubleshooting. It will be necessary to have a qualified technician locate the cause of the problem, which may be either a problem with the capacitor, the selector switch or the motor itself.

The unit rattles loudly when it turns off
The compressor in all window air conditioners is a powerful motor. When it starts up - and especially when it shuts off - the whole air conditioner can shake, sometimes loudly. Usually there is nothing that can be done to correct this problem. However, it is possible that the compressor mounting pads and brackets are worn out or missing. If that is the case the pads and brackets can sometimes be ordered and replaced.

Be sure that the air conditioner is securely mounted in the window frame if the unit shakes at all. It is possible for the unit to shake free of the frame if not installed properly.

Water leaks out the front of the unit
It is normal for water to collect in the lower base of an air conditioner. See the section entitled: "There is water sloshing around inside." If water leaks out the front it is usually because the unit is tilted forward in the window frame. All air conditioners should be installed so they tilt slightly back to allow for proper removal of the condensation collected.

The air smells musty
Air conditioners remove moisture from the air. The water collects in the base of the unit. Under normal conditions this water will be evaporated out of the unit. However, it is possible for some water to sit stagnant in the base of the air conditioner for extended periods of time. There is no easy way to prevent this problem. The problem will be reduced if you carefully clean the base of the inside of the air conditioner at least once a year. That will keep any dirt, lint or dust from absorbing the water and allowing mold and mildew to grow. Also, replace the filter behind or in the front cover.


Replace/clean filter every month
Air conditioners are outfitted with a simple electrostatic filter in the front grill area to filter the air that passes through them. If your unit has a filter you should replace/clean it once a month during the cooling season. You can purchase Electrostatic filter cut-to-fit material from our site.

Inspect cooling coils for frost or ice build up
If the temperature outside the room where the air conditioner is placed becomes cool, approximately 60 degrees Fahrenheit or lower, check the coils on the front of the air conditioner to be sure they are not icing up. If they are icing up, turn the air conditioner off until the temperature rises. Also, make sure the filter is clean.

Don't short cycle the cooling system
Air conditioners have a cooling system identical to a refrigerator's. It is important not to turn the unit off and then back on right away. Wait at least ten minutes after shutting the unit off to allow the pressure in the refrigeration system to equalize once again. This will prolong the life of your air conditioner.

Store the unit in a basement or utility room, not a garage
Mice and other small animals love to nest in air conditioners. If they do they can cause serious damage to the unit by chewing on wiring and insulation. Also, wasps and birds like to nest in uncovered units left in windows. Avoid these problems by storing the units in a protected area, away from small animals, or by installing a cover on the part of the air conditioner that sticks outside.

Clean condenser coils annually
The condensing coils on an air conditioner will get very dirty over time. However, the dirt tends to accumulate on the inside of the coils, out of site. It will be necessary to remove the entire cover of the air conditioner to gain access to the coils. They can be cleaned by blowing compressed air at them or by using a soft bristle brush to wipe the dirt off. It is important to also clean any dirt or lint build-up in the bottom of the air conditioner so the condensate water will be picked up by the condensing fan slinger properly.

Preventive Maintenance for portable or window air conditioners
HVAC Oracle

Portable or window air conditioners are an excellent choice for cooling a single room or and area where ducting cannot be used. Regularly is still required for best performance from these small units.

The evaporator coil on the cool side should have a thin foam filters covering the face of the coil. The Filter should be removed and cleaned regularly. Once a month should be sufficient. These filters do not hold dirt well; if they are allowed to get dirty the dirt will pass through to the evaporator where it is harder to remove. If the coil face has become dirty, brush the coil face off with a soft nylon brush. Dirt allowed to build on the coil will become trapped between the fins and reduce the air. This will reduce the cooling capacity and can cause the coil to freeze.

On the other side, the condenser coil has no filters; it can get very dirty depending on the environment that it is running in. Flush out the coil with water at the start of each season, before it is installed. This will help to prevent the unit from overheating on the hottest days of the year when you need it the most. The dirt builds on the air inlet side of the coil, which normally cannot be seen. If you want to see how dirty the coil is you have to remove the outer cover to see the air inlet side of the coil. Remove the screws spread out along the sides of the air conditioner, and lift the cover. With a flash light look at the air inlet side of the condenser coil, through the fan blade. By spraying water from the outside of the coil with hose or pressure water you can push the dirt back out through the coil. If using a pressure washer is used, spray straight onto the fins and stay at least 12 inches away. A pressure washer can flatten the fins very quickly is you get to close. When cleaning, be careful not to spray water directly onto the motor or electrical compartment. Use a plastic bag to cover up any vent holes on the fan motor. Allow the unit to dry out for several hours before installing and plugging the unit in. Place the unit on an angle to allow the water to drain back to rear. Any water left in the bottom of the tray is going to spill directly down the front of your shirt when you pick up the AC.

Depending on the size of the unit, there will be 1 or 2 fan motors. Most of the small units use a single multi speed double-shafted fan motor for both the condenser fan and evaporator fan wheel. Give the wheel a spin, does it feel tight or does it spin freely. Does the shaft move vertically? Any vertical movement, up and down, indicates worn bearings. If the bearings are tight or there is movement, use a little extra oil to loosen the bearing up. The fan may run still and be noisy, but it will quit. With the price of new portable AC so low and labor being expensive you are better of to replace the whole unit then trying to change the fan motor. Functional replacement motors are available for most units if you want to try and change it. Look at the ends of the motor for oil ports. If there are no oil ports then the motor has sealed bearings and cannot be lubricated. If there are oil ports add a few drops of SAE 20-, which is lightweight electric motor oil with no detergent added. The recommend oil amounts are normally on the motor nameplate, if you can read them. Look around the outside of the fan blades is a slinger, which is used to throw the condensed water from the evaporator coil up onto the condenser coil. This help to eliminate the condensate water and provide additional cooling to the condenser coil. This slinger sits very close to the edge of the fan shroud, even a slight misalignment will cause this to rub and make the unit noisy. With the top casing remove the unit can shift a little and cause the fan wheel to rub the edge, make sure the unit is sitting on a flat surface and well supported.

The electrical wiring on the unit should be inspected for any signs of burning or over heating. Check the tightness of all the electrical connections, any loose connection will overheat and burn, which can cause the fan or compressor to fail. Remove the retaining clip on the compressor terminal cover. The gasket under the cover keeps moisture out of the terminal connections. The compressor can sweat when operating and the moisture can drip down into the terminal connections and cause corrosion. The molded electrical plug of the unit is a common area for electrical problems. If the forks are loose or discolored, replace the plug. After the unit is installed and operating and on a hot day, check the temperature of the plug and wall receptacle. If it feels very warm then there is a connection problem or a low voltage. This can be a serious fire hazard There should be a vent flapper near the discharge of the fan. This should have a cable attached to open and close the vent. The vent when open will exhaust air to the outside, this helps to keep the air fresh in the room. The air expelled by the AC will be drawn in elsewhere through air leakage in the room, eventually exchanging the total volume of the room.

When replacing the casing on the unit use extra caution around the condenser coil. The screws near the condenser may be shorter than the other. If the screw is too long you can puncture the condenser coil and release the refrigerant. Give the fan wheel a spin to make sure it is rotating freely. If you hear it rubbing, take the case off and check the position of the condenser coil and the fan wheel again. Adjust as required.

After the units has dried out, plug the unit in while still on the workbench to give it a test run. The work area must be above 70%F else the thermostat may not make to start the unit. First run the fan only and check all speeds- Does the motor sound quite- is the fan rubbing on anything at high speed or low speed?

Next turn the compressor on by lowering the thermostat or switch to cool mode. Listen to the compressor start. Does it start right away or does it hum then start or does it talk more then a 2 seconds to come up to speed? The compressor should start right away and sound smooth. A slow start may indicate bearing wear I the compressor or low voltage. Low voltage can be cause by using an under sized extension cord. If you are using an extension cord make sure it is a minimum #14 gauge wire and less then 50 feet long. If the compressor is loud or have a rattle, this may indicate worn valves and reduced pumping capacity.

If you are running the unit without the faceplate, air can short cycle from the discharge back into the intake of the evaporator. Place a piece of cardboard to deflect the air up and it does get sucked back into the unit. With a good thermometer measure the air discharge temperature. It should be ~15%F less then the room temperature. This varies depending on what fan speed you are using. The higher the fan speed the lower the TD, at low speed the TD will be higher 20%F or higher. A TD of 10%F or less indicates a problem. This could a low refrigerant charge, overcharged, weak compressor, high head pressure or a clogged capillary tube.

If all has checked out then your AC is now good to go, install the unit in the window or sleeve opening. Make sure the unit is secured in the window and has a slight slope to the back to allow for drainage. Wall mounted and window mounted units have a different configuration. The window mount units are design to sit in thin profile of the window. If used an opening cut into a outside wall, the condenser air intake will be partially blocked. Cutting off air to the condenser, which will causes the unit to run hot. This reduces the amount of cooling, increase the energy use and on a really hot day, the compressor will quit or the breaker will trip.

After the AC has run for an hour, check that unit is draining out the back or the water is collecting in the condenser fan area. You should be able to hear the water in the condenser fan.

Remember to periodically check for the water is draining out the back and feel the electrical plug and receptacle area for heat build on the really hot days. Do not run the AC when it is cool outside, especially on cool clear nights when the outdoor temperature can really drop. This often causes freezing of the evaporator coil. Pull the filter out once every 4 weeks and rinse it out with water. That's it, the unit should be good for the season.

Keeping your cool no matter how hot it gets.
Summer's here and your room air conditioner is laboring hard. You can help the appliance work more efficiently through the months ahead by following a simple maintenance program, and you might even save a little money on your utility bill.

Effectively keeping up some appliances -- high-efficiency gas or oil furnaces, for example--requires a technician. Fortunately, a basic room air conditioner can be maintained by a homeowner who has only a few hand tools and a shop vacuum.

To begin, unplug the air conditioner and remove the front grille and filter (Figs. 1 and 2). The filter traps pollen, dust and dirt, and if it's clogged, you won't get maximum cooling performance. Wash it with a mixture of warm water and soap. If the filter has deteriorated, replace it. Your local appliance store, hardware store or home center may be able to supply you with the exact size and type of replacement part you need. If not, several manufacturers make filters that can adapt to many brands of air conditioners. These are cut to fit with a pair of scissors. One source for such filters is the General Electric Consumer hotline: (800) 626-2000. A cut-to-fit GE filter costs $8.05 with shipping (state tax is extra).

Remove the air conditioner from the window and clear away any accumulated debris from the windowsill. Take the appliance out of its cabinet. (Some will slide out of the cabinet, but on most, the cabinet is held in place with screws.) Remove the screws and put them aside (Fig. 3). Then, use a shop vacuum and crevice tool to get rid of leaves and debris from within the air conditioner (Fig. 4).

To clean the inside (Fig. 5), bring the appliance outdoors and use a paintbrush and some soapy water. Put plastic bags over the fan motor, electrical control box and compressor. Secure the plastic with duct tape. Hose the inside clean (Fig. 6), and make sure the base, coils and pan for condensate are clean as well.

When you've finished, remove the plastic bags and dry off the air conditioner with a fresh cloth. Allow the remaining moisture to evaporate, or you can accelerate the drying process by blowing out moisture with a can of compressed air. Single-use cans of compressed air are available through tool catalogs and some hardware stores. You can also try using a rechargeable air tank, which is sold at hardware stores, home centers and auto parts stores.

When the appliance is dry, reassemble and reinstall it in the window, following the general guidelines mentioned below. It's a good idea to allow the air conditioner to remain idle for one full day--just to be sure that the machine is thoroughly dry before you begin running it.

Now that the maintenance of your air conditioner is complete, it's time to start thinking about ways of getting maximum performance and durability out of the appliance.

Many people mistakenly believe that air conditioners need to be pitched down, slightly out of level, to help them drain condensate. Actually, the exact opposite is true. An air conditioner should be installed so it's level. These appliances are designed so that condensate collects below the fan and runs into the slinger ring, which is made of sheetmetal and is part of the fan assembly. The bottom of the ring acts like a gutter to collect condensate. The fan then picks the water out of the ring and slings it against the condenser coils.

Recycling the condensate in this manner increases the coils' cooling capacity. Check the air conditioner for level -- front to back and side to side -- when you install the unit.

If the appliance's side panels are cracked, now is the time to replace them. In some cases, you can get a single side panel from an appliance store (each side costs about $15 to $30), or you may have to buy both sides -- and the guides that they run in. Some people opt not to replace the side panels when they wear out. Instead, they remove the panels and screw clear plastic sheet (Plexiglas, for example) over the runners. This also lets in a little extra daylight.

Take steps to seal the area where the window closes on top of the air conditioner. In many instances, the foam strip that came with the appliance will have worn out. The gap left by an improper seal is energy inefficient, not to mention an entryway for bugs. Appliance stores sell kits called Air Conditioner Window Foam. These are nothing more than bags with foam strips that have peel-and-stick backing. If you can't find one of these kits, you may substitute adhesive-backed weatherstripping. Weatherstripping can also be used as a vibration damper when a storm window or screen rests on the top of the appliance.

If your air conditioner is installed in a vinyl replacement window, think about using a wood reinforcement strip below the appliance to distribute its weight. An air conditioner is heavy enough to distort some vinyl replacement windows. Also, consider screwing L-brackets into the window channel rather than letting the unit rest against the window sash. Again, the brackets bear the weight of the air conditioner -- not the replacement sash.

If you have a problem with birds building nests under the air conditioner, install a thin, exterior-grade strip of plywood or a piece of painted solid wood to block their entry.

Operation Tips
Finally, there are things you can do to help reduce the heat load on your air conditioner. One sounds obvious, but it's often overlooked: Draw blinds or drapes on the sunny side of the house to block out the Sun's rays. In hot, sunny climates, awnings can also substantially reduce heat gain. Further, keep the garage door shut and close all the windows in the house.

Along similar lines, the same kinds of weatherstripping that prevent heat loss in the winter also prevent heat gain in the summer. Properly weatherstripped doors and windows, combined with attic insulation, are your best defense against wasted energy.

And don't overlook ventilation. Attic, ridge and soffit vents should be cleared of bird and insect nests so that attic heat can escape.

Winterizing your air conditioner at the end of the season is simple. If you leave it in the window, wrap it with plastic sealed with duct tape, or buy an air-conditioner cover. With stay-in-place machines, also remember to close the vents. If you take the appliance out of the window, be careful not to bend or damage the cooling fins on the back of it. And don't store an air conditioner on a garage floor, where it could come into contact with corrosive de-icing salts that can drip off of a car's tires.

How-to Photos

1-- The first two steps in air-conditioner maintenance are unplugging the appliance and then removing its front grille.
2--Remove filter and wash it thoroughly. If filter particles come loose, or if the part is cracked or has many holes, replace it.
3--Next, remove the side panels from the air-conditioning unit, then take out the screws that are holding the cabinet.
4--Use a shop vacuum and crevice tool to clean any dust and debris that may have accumulated inside the air conditioner.
5--Cover all electrical components with plastic bags. Then, clean the inside of the unit with soapy water and a paintbrush.
6--Hose down the appliance and let it dry. Reassemble and reinstall it, but wait a day to make sure it's dry before turning it on.

Filter maintenance is the #1 forgotten thing to do on a room air conditioner. Please read the Repair Air sheet below...

Some simple things to check for before calling for service...

Helpful parts, accessories and links dealing with room air conditioners.

Window air conditioner mounting brackets Mount your window air conditioner properly and securely with A/C Safe's installation kits.

Heavy gauge steel with baked on epoxy finish plus stainless steel hardware ensures good looking, long lasting performance. Unique bubble level insures installation at the correct angle every time.

A/C Safe window air conditioner mounting kits available for several unit weights including up to 80 or 160 pounds.

Universal curtain accordion panel kit
Air conditioner side curtains often become brittle with age, cracking and leading to air leakage. Replace broken, cracked or discolored accordion filler panels with 'universal ' cut to fit replacements.

This universal kit can replace existing accordion panels measuring up to 21 inches by 12 and come 2 per package and include installation material.

Universal side curtain and frame kit
Old curtains simply too far gone for just replacement accordion inserts? Try a complete universal side curtain and frame kit.

This kit contains both left and right side curtains plus top and bottom rails to replace a units existing parts or retrofit a through-the-wall type unit for window use.

Replacement A/C filterKeep your air conditioner working its best by cleaning or replacing the filter behind the front grill frequently. This 24 by 15 inch cut to size replacement filter will fit most models that did not originaly have an attached molded, rigid plastic frame.

Air conditioner blower fan motor The fan motor on air conditioners will need to be replaced occasionally. These motors are so varied that finding an alternate to the factory replacement is usually very difficult, if possible at all. You can help prevent motor failure by oiling serviceable motors with an appropriate lubricating oil each season.

'Zoom Spout' oiler with telescoping spout Many motors used in air conditioners have oiling ports that should be oiled twice a year, once each year before the unit is installed and once before winter storage.

The 'Zoom Spout' oiler is perfect for this since the wax free oil ensures that the motor bushing's pores do not get clogged and contribute to premature component failure. The retractable 8 inch spout helps you get to all those hard to reach places like the oiling ports found on many larger motors and the motor bushings found on smaller ones.

Air Conditioner Capacitors

Fan motor and compresor capacitors There are two critical specifications that need to be identified when looking to replace an air conditioner's fan or compressor run capacitor, the voltage and the capacitance rating in microfarad (uF or MFD). The physical size and shape (round/cylindrical or oval) is irrelevant except for mounting considerations and you will often find newer capacitors considerably smaller then old ones of the same rating.

As a replacement you can use an alternative of a higher voltage rating without any problems but the capacitance should be within 10 percent of the original but an exact replacement is always best.

Some models may utilize a 'dual' capacitor where the compressor and fan motor capacitor are built into one. On this type you will see 3 groups of terminals across the top of it. There will be one set of common terminals, one group for the fan motor and another for the compressor wiring.

Fan motor and compresor capacitors The common terminals on a dual capacitor will usually be indicated with the letter "C" near the associated terminal set, the fan side may or may not be indicated. The compressor will almost always be indicated with the word "herm" (short for hermetic) indicating part of a hermetically seal system (which the compressor is part of).

Dual capacitors are usually considerably more expensive to replace than single purpose ones.

Air Conditioner Controls

Thermostat (temperature control) Mechanical (non-electronic) room air conditioner thermostats come in many shape and sizes. There are typically 2 mechanical types:

  • Hydraulic, which have a capillary tube (sensor bulb) that mounts in the air stream (usually in front of the evaporator coil) to sense the air temperature and
  • Bimetal, that have an internal bimetal disk or hydrolic air-coil that reacts to the change in temperature where the thermostat itself is situated.

Although there are some adaptable (universal) replacements that are available, to ease in installation and keep the original appearance of the appliance, you should always try to use the original factory replacement whenever possible. However, on older models where finding original replacement part may not be possible, a universal replacement may be an alternate choice.

Push button selector switch Selector switches also come in several styles: rotary and push button. It is usually very difficult to find any kind of after market replacements. In this case, the genuine factory replacement part will likely be your only available option when replacement becomes necessary however the link below lists some universal rotary type selector switches that may work if no original is available or can be located.

Do not drill holes to remove excess moisture from inside the unit. The water that accumulates in the bottom is the humidity removed from your room. On many models, the condenser fan blade picks up this water and throws it on the hot condenser. When it evaporates it aids in the heat removal from the refrigerant. In addition, the refrigerant gas travels in thin copper tubing easily punctured. Expensive repairs will be required to fix it and that damage will not be covered by any warranty.

Do not attempt to use regular plumbing solder to repair copper or steel refrigerant lines. This requires special silver-alloy solders such as Silfoss or silver solder to withstand refrigerant pressures. In addition, once tried, it may not be possible to remove the household solder to weld the lines properly.

Keep the front grill on the unit. Proper air circulation is necessary for highest efficiency. Also make sure curtains or other obstacles do not hamper the air flow.

Keep other window curtains closed as sunlight can increase room temperature greatly. If possible put the air conditioner in a north facing window to avoid direct sunlight on the condenser because it will hamper heat removal.

Do not operate the unit on an extension cord! The compressor draws a lot of current and can be damaged if insufficient voltage is continually supplied. If you must use one, use only those designed for air conditioners (usually flat) AND only as long as required. NEVER use a lawn mower extension cord.

Air conditioners are not meant to be operated if the inside or outside air temperature is below 70°F. If this happens, ice will form on the evaporator coil and will restrict air flow possibly burning out the fan motor. If the temperature is suppose to drop during the night, set to thermostat to a warmer setting to allow the compressor to cycle off when necessary to avoid icing up.

Have your unit steam-cleaned at least every 3 years, every year if you live in a heavy traffic area. Particles stick to the surface of the condenser, reducing the cooling efficiency and causing increased power consumption. This is also true for central air conditioners.

When installing a window or through the wall air conditioner, it is important that it still be removable. It will need to be removed for repairs and the periodic maintenance that is required from time to time. It is also important that none of the air louvers on the sides be blocked. Reducing these air vents will reduce the cooling ability of the unit and can lead to premature component failure. Any failures caused by this will usually not be covered by any warranty.

To aid the flow of recovered room humidity from the front of the cabinet towards the rear, make sure that the unit is pitched so that the rear of the unit is 1/4 to 1/2 inches lower than the front.

Steve & Barbara Arnold
11506 Seatonville Road
Louisville, KY. 40291

Problem #1: Outdoor condensing fan motor has stopped running. This problem could be caused by a bad motor run capacitor. Please see our Run Capacitor Page to purchase a new capacitor. Here is a link to our capacitor page: Please click here for Motor Run Capacitors. If your motor capacitor is not the problem, then more than likely you need a new motor. We do not sell condenser fan motors. Is the fan blade tight, stiff or hard to turn? If the fan blade is hard to turn then you probably need a new motor.

Problem #2: Air conditioner compressor will not start. When power is applied to the air conditioning outdoor unit the fan starts, but you hear a sound like the compressor is trying to start, "UGGG"..., for about 5 to 10 seconds and then all you hear is the outdoor condenser fan run. The compressor is locked and will not start. What is happening is the compressor is trying to start, but because the compressor motor is locked it tries to start for a few seconds and then because of the high amperage being drawn goes off on internal overload. The internal overload protects the compressor windings from overheating and burning up. I see this many times during the start of the air conditioning season. Some compressors just have a hard time starting after sitting all winter long. Some compressors are locked up so bad that I can not start them and must tell my customer that they need a new compressor or new air conditioning system. Many times I can get the compressor started again without having to buy a new compressor or new air conditioning system by using the device that I sell below. It is called, "Super-Boost." I keep two or three of these on the truck. They have saved many of my customers from having to buy new air conditioning systems. Below is a description of the "Super Boost" with an opportunity for you to purchase.

The Super-Boost could save you from having to purchase a new air conditioning compressor or system!

The Supco, Super-Boost has the following features that make it a life saver when it comes to air conditioning repair:

  • The Supco can save stuck compressor by increasing the compressor's starting torque by 500%.
  • The Supco, Super-Boost is a solid state relay and hard start capacitor no loose parts or complicated wiring. Just wire it across your run capacitor as shown below.

    On dual capacitor systems just connect between the "C" and "Herm" terminals. Please see picture below:

  • The Super-Boost can be used on all PSC single phase 115 volt thru 288 volt air conditioning units from 4,000 to 120,000 BTU.
  • It can be used on a wide range of air conditioning compressors from 4,000 BTU window units to 10 ton commercial units.
  • The Supco Super Boost is used for tight or locked compressors, if you have low voltage, or for quick recycling of the compressor.

Below are pictures with an opportunity to purchase. Thank You!

Problem #3: This problem is probably the second most common problem that I see every summer. The problem is a bad compressor or fan run capacitor. The Air conditioner outdoor unit will not come on. Either the outdoor fan does not run, the compressor does not run, or both the fan and the compressor do not run. You checked and reset your breaker and the outdoor unit still does not come on. You can hear a little humming sound, sometimes a "Uggg" inside the unit when power is applied. The "Uggg" is the compressor trying to start. You might hear the low voltage contactor humming. You pull the disconnect and disconnect the power to your outdoor air conditioning unit. Please make sure your electrical power is off before working on any air conditioning equipment. You take the door or cover off your outdoor unit's control box and find a bad, swollen run capacitor. EPA stopped allowing manufacturers to produce capacitors with cancer causing PCB's. Since they stopped allowing the use of PCB's the capacitors now have a shelf life. Many times I see capacitor problems that will not allow the compressor or the fan to come on. Many times you can clearly see that the capacitor is bad because it is swollen or even blown apart with capacitor oil everywhere! Sometimes you need a special meter to test the microfarad (MFD) rating. Most of the time you can tell the capacitor is bad because it is swollen up. Please see the picture below for the comparison between a good and bad dual run capacitor. We call them, "Dual" because the capacitor helps run both the fan and the compressor.

Bad round dual capacitor on the left. Good round capacitor on the right.

Bad oval capacitor on the left. Good oval capacitor on the right.

Solution: You need to purchase a new capacitor. We have many different types of capacitors listed on our Run Capacitors Page

Hard Start Kit for Normally Stuck Compressors.
Frozen or stuck air conditioning compressor? Before you spend hundreds of dollars come look at these! They work 50% of the time.

If you think your compressor needs more torque to break it loose please order the Hi Power Start Kit.

If you have been told that your air conditioning or heat pump compressor is stuck or in other words mechanically frozen and that you need a new compressor which costs hundreds of dollars, look this Hard Start Kit over! This kit may start the compressor, but mechanically frozen compressors may still need to be replaced, however these are worth a try. These units work 50% of the time. If your compressor is REALLY stuck you may need to order the Hi Power version on the Category Page?? No body knows how stuck it is, so you be the judge!

This is the item that no H.V.A.C. Contractor wants you to know about!

This device installs with (2) wires. One wire goes to the RUN side of your compressor run capacitor and the other wire goes to the START side of the compressor Run capacitor. ( Follow the large wires that come out of the compressor until they end up at the large RUN capacitor for the compressor ). Shut the circuit breaker off at your main electric panel, if you aren't sure which one it is then shut them all off. There may be more than one breaker. Once you are sure the 230 Volt power is off to the Air Conditioner or Heat Pump you will need to Dis charge the compressor run capacitor by shorting it's terminals out to a bare metal part of the cabinet with an insulated tool such as a screwdriver. These capacitors store a high amount of power which will give a nasty shock. While it won't kill you, it does hurt! See the picture below for a typical run capacitor made for just the compressor, it will have only 2 terminals. One wire of the Hard Start Kit goes to one terminal the other wire of the Hard Start Kit goes to the other terminal. If you have a Dual Rated capacitor you will see (3) terminals marked Herm, Fan and C. This Hard start kit goes to the "C' and Herm terminals. The fan terminal is for the condenser fan do not use this terminal. These Dual Rated Capacitors run the compressor and the fan with just this one capacitor.

Hard Start Kit for Extremely Stuck Compressors.
Frozen or stuck air conditioning compressor? Before you spend hundreds of dollars come look at these! They work 75% of the time.

If you have been told that your air conditioning or heat pump compressor is stuck or in other words mechanically frozen and that you need a new compressor which costs hundreds of dollars, look this Hard Start Kit over! This kit may start the compressor, but mechanically frozen compressors may still need to be replaced, however these are worth a try. These work 75% of the time! The unit we sell below is the largest of the Supra Hard Start Kits and supply OVER 600% increase in starting torque! If this unit won't start the compressor we know of no other start kit that will!

This is the item that no H.V.A.C. Contractor wants you to know about!

This device installs with (2) wires. One wire goes to the RUN side of your compressor run capacitor and the other wire goes to the START side of the compressor Run capacitor. ( Follow the large wires that come out of the compressor until they end up at the large RUN capacitor for the compressor ). Shut the circuit breaker off at your main electric panel, if you aren't sure which one it is then shut them all off. There may be more than one breaker. Once you are sure the 230 Volt power is off to the Air Conditioner or Heat Pump you will need to Dis charge the compressor run capacitor by shorting it's terminals out to a bare metal part of the cabinet with an insulated tool such as a screwdriver. These capacitors store a high amount of power which will give a nasty shock. While it won't kill you, it does hurt! See the picture below for a typical run capacitor made for just the compressor, it will have only 2 terminals. One wire of the Hard Start Kit goes to one terminal the other wire of the Hard Start Kit goes to the other terminal. If you have a Dual Rated capacitor you will see (3) terminals marked Herm, Fan and C. This Hard start kit goes to the "C' and Herm terminals. The fan terminal is for the condenser fan do not use this terminal. These Dual Rated Capacitors run the compressor and the fan with just this one capacitor.

Below are some typical run capacitors. Shown are round capacitors, there are also oval run capacitors used in many systems. The ones with (2) terminals require (1) capacitor for the fan motor and still another for the compressor. Dual rated capacitors have (3) terminals and only need (1) capacitor as the fan and compressor run off just this (1) capacitor.


Item pictured below is not the SPP7S model and is for demonstration purposes only. The SPP7S is similar however.

PCMTL.com is the web's best resource to get free Air Conditioner repair advice for all major brands of Air Conditioners including Admiral, Airtemp, Amana, Climatrol, Emerson, Estate, Fedders, Frigidaire, GE, Gibson, Goldstar, Hampton Bay, Hotpoint, JC Penney, Kelvinator, Kenmore, Marta, Panasonic, Quasar, Roper, Tappan, Westinghouse, Whirlpool, White-Westinghouse, and more.