Central air conditioners have two separate components: the condenser and the evaporator. While there aren't many repairs you can make yourself, there are specific maintenance procedures you can follow to keep your system operating at peak efficiency. Caution: Before doing any work on an air conditioning system, make sure the power to the system, both to the condenser and to the evaporator assembly, is turned off.Before you start working, let's try to narrow the scope of the job. Look for the problem you're having, and its solution, on the chart on the next page.For more articles on home repair, check out the following links. How to Test a Thermocouple on a Gas ValveShow All ItemsStep 1: freon checkShow All Items You will need a set of manifold gauges to check you freon pressure. Here are some general guideline for A/C system pressures and temperatures based on ambient outside temperature. Remember that these are a guideline and your actual temperatures and pressures will vary depending on humidity in the air and the condition of your system.

When running the car at idle to check the freon level it is a good idea to have a water hose handy and spray water on the a/c condencer. The condencer is located in front of the radiator. For vehicles currently running with freon R-134a onlyOutside-----low side-------High side------Center vent temp 60 F -----28-38 psi----130-190 psi ----44-46 F 70 F ------30-40 psi ---190-220 psi ----44-48 F 80 F ------30-40 psi ---190-220 psi ----43-48 F 90 F ------35-40 psi ---190-225 psi ----44-50 F100 F -----40-50 psi ---200-250 psi ----52-60 F110 F -----50-60 psi ---250-300 psi ----68-74 F120 F -----55-65 psi ---320-350 psi ----70-75 F_You can also use this good rule of thumb with R134acleaning an air conditioner wall unit, run fan on High with all windows open and engine at 1500 rpm. ac with two indoor unitsHigh side pressure in PSI should be about 2.2 to 2.5 times outside air temperature in degrees F. Example if it's 90 degrees F, high side should be no higher than 225PSIHere is a useful trouble shooting chart for systems currently running on freon R-134aTrouble shootingLow Compressor Discharge Pressure1. the best split air conditioner brand

Leak in system 2. Defective expansion valve 3. Suction valve closed 4. Plugged receiver drier 6. Compressor suction valve leaking 7. Bad reed valves in compressorRepair1. Repair leak in system 2. Replace reed valvesHigh Compressor Discharge Pressure1. Air in system 2. Discharge valve closed 4. Insufficient condenser air 6. Loose fan belt 7. Condenser not centered on fan or too far from radiatorRepair1. Remove some refrigerant 5. Install large fan 6. Tighten fan belt 7. Center and check distanceLow Suction Pressure1. Worn compressor piston 3. Compressor head gasket leaking 4. Kinked or flattened hose 5. Compressor suction valve leaking 6. Moisture in system 7. Trash in expansion valve or screenRepair1. Replace head gasket 4. Change valve plate 6. Replace drierHigh Suction Pressure1. Loose expansion valve 2. Expansion valve stuck open 4. Compressor reed valves 5. Leaking head gasket on compressorRepair1. Remove some refrigerant 3. Replace expansion valve 4. Replace reed valves 5. Replace head gasketCompressor Not Working1.

Broken clutch wire or no 12v power 3. Broken compressor piston 4. Bad clutch coil 6. Low Refrigerant - low pressure switch has cut off clutch powerRepair1. Repair wire or check for power 3. Replace clutch coil 6. Add refrigerantEvaporator Not Cooling1. Frozen coil, switch set too high 2. Drive belt slipping 3. Hot air leaks into car 4. Plugged receiver drier 5. Capillary tube broken 6. Shortage of refrigerant 7. High head pressure 8. Low suction pressure 9. High suction pressure 10. Defective expansion valve 11. Turn thermostat switch back 2. Check for holes or open vents4. Replace expansion valve 6. See problem #2 8. See problem #3 9. See problem #4 10. Replace expansion valve 11. Evacuate and replace drierFrozen Evaporator Coil1. Thermostat not set properly 3. Set to driving condition 3. Check for excessive duct hose length, kink or bend.If you can't get your a/c to turn on then use this chart to determine if you are low on freon. Remember that this is a general char and will very for different makes and model cars and refrigeration units Temperature -------------------134a Pressure(Psig) -60.0----------------------------------21.6* -55.0 -----------------------------------20.1* -50.0 ---------------------------------- 18.5* -45.0 ----------------------------------- 16.7* -40.0 ----------------------------------- 14.6* -35.0 ----------------------------------- 12.3* -30.0 ----------------------------------- 9.7* -25.0 ------------------------------------ 6.7* -20.0 ------------------------------------ 3.5* -15.0 ------------------------------------ 0.1 -10.0 ----------------------------------- 2.0 -5.0-----------------------------------------4.2 0----- ------------------------------------- 6.5 5.0 ---------------------------------------- 9.2 10.0 ----------------------------

--------- 12.0 15.0--------------------------------------15.1 20.0 --------------------------------------18.5 25.0 ------------------------------------- 22.2 30.0 --------------------------------------26.1 35.0 --------------------------------------30.4 40.0---------------------------------------35.1 45.0---------------------------------------40.1 50.0 --------------------------------------45.5 55.0---------------------------------------51.2 60.0--------------------------------------- 57.4 65.0----------------------------------------64.1 70.0--------------------------------------- 71.1 75.0 ---------------------------------------78.7 80.0--------------------------------------- 86.7 85.0--------------------------------------- 95.3 90.0 ------------------------------------ 104.3 95.0--------------------------------------114.0100.0 -------------------------------------124.2105.0--------------------------------------135.0110.0--------------------------------------146.4115.0--------------------------------------158.4120.0--------------------------------------171.2125.0--------------------------------------184.6130.0--------------------------------------198.7135.0------------------------------------- 213.6 140.0--------------------------------------229.2145.0 ------------------------------------- 245.5150.0-------------------------------------- 262.9155.0-------------------------------------- 281.1160.0---------------------------------------300.0- (in Hg) Vacuum« PreviousNext »View All Steps Download