Question about 1995 Cadillac DeVille
Ac wont come on. full of refridgerant but does nothing
To diagnose problems, an A/C manifold gauge set is needed to read high and low side pressure readings. Avoid adding refrigerant with a simple charging kit like the ones sold at parts stores. Don’t add any stop leak, this can cause problems in the compressor, expansion valve or condenser.
Keep in mind that using an A/C gauge set and seeing BOTH high and low side readings can help in diagnosing the problem when you know what to look for. First, on a 134A system the high and low side service ports are different sizes. AC gauge sets have color coded hoses, the blue color coded hose has a connection that fits on the low side service port and the red hose has a connection that will only fit onto the high side. The yellow hose won’t hook up to anything if just checking the readings; it can be used to connect to a vacuum pump or attached to a refrigerant can or tank.
Normal readings on high and low side with AC OFF (static pressure) - Depends on outside temperature, but normally is between 80-105 PSI
Normal low side reading with AC on high speed and MAX & engine at 800-1000 RPM’s - Ranges from 25-35 PSI - Note that on many Chrysler products a normal reading on the low side may be 15-25 PSI
Normal high side reading ranges from 200-350 PSI
Don’t assume that if adding little Freon is good that adding a lot is better! Overcharging just a little can decrease the performance of the system and possibly damage the compressor.
Both low and high side readings are lower than normal, this indicates a cars AC system is low on refrigerant and is under-charged.
If both low and high side readings are too high, this indicates an overcharged system - too much refrigerant. This also can indicate that the condenser fan is not working, is too slow or the car is overheating and heat is transferring from the radiator to the condenser.
Good luck and hope this helps, keep me posted be glad to answer any question you may have. And yes the A/C system on your car uses R143a and there is a A/C pressure switch along the low pressure line or on the accumulator, it looks like a oil pressure sensor with a two wire lead cliped on it.
Posted on Jul 02, 2009
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