Q--I have an '89 Toyota Corolla, which I bought in '95. The air conditioning worked perfectly, with much use, until this year. Suddenly, there was no cool air. My mechanic put in Freon and that lasted for about five tries. There were no obvious holes or cracked hoses. What should I check? There was no gradual loss of cooling power. One day it worked; the next day it didn't. J.B., ChicagoA--There need not be obvious holes or leaks for the refrigerant--Freon--to leak out. Often, it does so without a trace, but your technician can use a tracer dye to pinpoint the leak. An ultraviolet dye is injected into the air-conditioning system along with some refrigerant and the A/C is run for a while. Shining a black light on suspected leak points will reveal them in fluorescent color.Some technicians prefer to use an electronic leak detector, which works just as well, if not better. There is not much you can check yourself.Q--We own a 1992 Cadillac Seville that we purchased new. All scheduled maintenance was performed on time at the Cadillac agency.

On several occasions while under warranty the passenger compartment was filled with a strong odor of raw fuel. We took the car in on more than one occasion, but the Cadillac service department could find no cause. They checked all hose clamps, etc.Now after seven years it still on occasion will fill the passenger compartment with a strong odor of raw gasoline. It does not necessarily happen after a tank fill. Could you advance suggestions on what might be the cause? A. M., ChicagoA--We suspect a problem with the vapor recovery system, which functions like a surge tank for the volatile gasoline vapors to prevent them from polluting the air.There is a canister filled with activated charcoal that traps the vapors until the engine is warmed up. Then the vapors are purged into the engine. A problem with the canister or purge system could release the vapors under the hood, which are then drawn into the interior via the fresh air intakes near the windshield.Also, avoid over-filling your fuel tank because this can saturate the vapor recovery tank with liquid fuel.----------Bob Weber is an ASE-certified Master Automobile Technician, having recertified every five years since 1978 and having worked at independent repair facilities.

Write to Motormouth, 17717 Silcott Springs Rd., Purcellville, Va., 20132. Send e-mail with name and town to MotormouthTribune@netscape.net. Answers will be supplied only through the paper. Reports Sought In Jonbenet's Sister's DeathColumbo`s WorldPain relievers: What are the differences?Try some sweet -- or sour -- reliefDark meaning of bubble-gum Pumped Up Kicks is tough to chew10 reasons why you want the jobShow 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 R134a

, run fan on High with all windows open and engine at 1500 rpm. High 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. cheap ac repair stockton caLeak in system 2. 2.5 ton ac unit cost carrierDefective expansion valve 3. ruud hvac unitSuction 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