Before you even consider taking your car to the shop just to see if your ac is ready for the season its best to do a quick check yourself. Its easy to perform a Car AC Check yourself with just a few minutes and a handy tool. You won't need any expensive Automotive AC Gauges for this test. The only tool you need is a cooking thermometer, besides yourself of course. Just place the Thermometer in the center vent on the console, set your ac to max cold and run the engine at 1,500 rpm for about 5 minutes and you should see about a 20 - 30 degree drop in temperature form the outside temp. If so, your good to go! If it fails the test, then its time to get out the auto ac gauges and be ready to check the auto ac pressures chart below.
FOR AUTO AIR CONDITIONING R134a SYSTEMS: At IDLE - Condenser inlet temp 170 to 180, Condenser Outlet temp 135 to 150 (usually a 30 to 40 degree drop in temperature across the Condenser), Evaporator Outlet temp 45 to 55, Compressor Suction temp 60 to 70 (usually a 15 to 20 degree drop in temperature from the evaporator outlet to compressor suction port). With the engine IDLING, you want to adjust the charge so the line at the Compressor suction port is about 10 to 20 degrees WARMER than the Evaporator Outlet pipe, and with the engine running at 1500 to 1800 rpm, you want the line at the Compressor suction port to be about 2 to 10 degrees WARMER than the Evaporator Outlet pipe. At 1500 RPM - Condenser inlet temp 190 to 200, Condenser Outlet temp 135 to 155 (usually a 40 to 60 degree drop in temperature across the Condenser), Evaporator Outlet temp 45 to 55, Compressor Suction temp 55 to 60 (usually a 7 to 12 degree drop in temperature from the evaporator outlet to compressor suction port).At 90 degrees ambient, for R134a systems, look for about 200- 220 Pressures on the high side and about 25-30 Pressures on the low side at idle, and at 1,500 RPM look for about 220- 230 Pressures on the high side and about 20-27 Pressures on the low side. The Compressor should cycle off at around 20 PSI.
Temperature Pressure (°F) (Psig) * - (in Hg) Vacuum
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