sounds like the thermostat probe is getting cold and forcing the ac to turn off. i have had that happen before. pull hte front off the unit and you will see a copper tube attached to the coils. pop it out gently and move it lower on the coil.

also make sure the coils are clean, both inside and outside. for the outside coil, spray it with a water hose to wash it out, the dirt is on the inside so it usually is not visible unless you totally disassemble the unit.

Hi,

Thanks so much! I'll try that when I get home and see if it has an effect.

Filter - what does the filter look like - may need to be replaced.

We are having the same problem with our older "WallMaster" unit by Friedrich. After cleaning both coils, filters, checking thermostat, etc finally broke down and called in a repair person. Sad news was that the compressor is going causing the unit to shut down before reaching the proper temperature.

Try all the above suggestions, especially cleaning the filter, and a through cleaning of the units coils (both).

Get a good thermometer (an instant read kitchen one will do), and check the difference between the incoming air (front of the unit), and what is being blown out. There should be at least a 12-20 degree difference. If the condenser comes on, but shuts down after about 10 minutes, you may have a problem with motor (condenser), in which case it would be cheaper to chuck the unit and buy new.

In fact considering how inexpensive units can be,you may wish to look into getting a new one sooner rather than later. The last thing you want to do is purchase a new unit during a heat wave because your current AC died a slow painful death. If funds are tight check Craigslist for local people selling units. They may not be what you want, but it will get you through the summer, that way you can wait and get a good deal when stores are clearing stock in the late Fall.

There should typically be foam strips either on the backside of the front grille or around the air discharge area to keep the cold outflow separated from the intake. If the foam is deteriorated or missing, cold output air can get sucked or directed back into the intake *behind* the grill which also will give the thermostat a false reading and cause short-cycling.

All motors use a capacitor and some kind of start relay if 110vac. This is similar to what a refrigerator uses. When the cap, relay or overvoltage is bad, it can short cycle or shut down until the compressor cools enough to allow it to restart.

Cleaning coils on a window unit requires dissembly of the unit. The inside of the outer coil needs to be cleaned, and the outside of the inside coil needs to be cleaned. I have seen dirty evaporator coils inside of the hidden part of the inside or evaporator coil many times. This normally requires dissembly of the cover plates to reach the coil. The outdoor coil will get heavy dirt buildup in the corners. This hurts the efficiency enough to shut down the compressor or even trip the circuit breaker.

In the past, when I cleaned a window unit, I liked to use the rear of the pickup. It was high enough that I did not have to bend over, and I could get water on the bed without damaging the truck. I liked to turn the AC unit on it's side to clean the pan. I like to allow a day or so to dry, and for the oil to settle inside of the compressor.