I have a 93 del sol si that I have had in the shop 4 times in the past 2 weeks for a/c problems. The safety pressure valve kept on popping and was replaced 3 times. Im on the fourth now and so far so good except for one small problem.

Let me backtrack tho so you know the whole situation. The a/c clutch froze on my car about a year ago and I decided I've had enough of the heat. I went in and had the compressor, clutch, and dryer replaced. The mechanic told me the expansion valve was fine so he did not replace it. Also it was recharged with r12 and is currently working to a point. When you first turn the car, meaning when the engine is cold, the a/c works flawlessly, but after the engine is to operating temperatures sometimes the a/c clutch will not engage and the engine rpms (while stopped) will hover around 1500 as if the clutch was engaged. I today replaced both relays meaning the fan relay and the clutch relay near the condenser but still have the same problems. Also I've noticed that when I am driving the compressor with turn on and off rapidly during both acceleration and maintained speed. Any advice would be much appreciated.

 

Have you tested the pressure switch?

 

No. How do I test it? and where is it located?

 

If it is like civics, should be on the dryer, unplug it and take an ohm meter touch each terminal should read 00

 

Sounds like the system is overcharged with refrigerant. Hook up a manifold gauge set and measure refrigerant pressures on the high and low sides with the engine idling at 1500 rpm. Post the pressures and the outside temp during the test.

 

Can I change this pressure switch without evacuating the system? also is it possible to change the thermostat without evacuating?

 

Ok. Do they still sell r12 gauges?

 

Do nothing with the pressure switch or thermostat until you have measured the refrigerant pressures. Yes, you can buy R12 or R134a/R12 gauge sets. Check auto parts stores to see whether they offer a free rental of the gauge set.

 

ok, ive called around and cant seem to find an r12 set for rent, but I am going to swing by a shop and borrow theirs hopefully.

 

Ron on the pressure switch there is a molex plug, you can unplug it and test it, will do no harm and no lose of freon.

 

I agree. I should have said don't replace the switch or thermostat until you have measured the refrigerant pressures.

 

Ok ran into a problem with a fuse the day that i needed to test pressures. The problem I have now is when moving at cruising speed the compressor turns on and off rapidly, or about every 10-15 seconds. While sitting at a light or slow speed sometimes the compressor does not turn on at all but the idle raises to 1500 acting as if the compressor were in fact engaged. No I have not tested pressures yet but my mechanic swears they are perfect. Ill have to try to snag a pair of gauges somewhere.

 

 

Overcharge

 

Found the problem yesterday. Hooked up a pair of gauges and while the car was at idle the pressure's were fine, but as you increased the rpms the expansion valve would stick cause the high side pressures to rise and the low side pressure to dip. Replacing the valve as we speak. Also the first mechanic told me the valve was fine, always better to do your own work I suppose. Oh and was overcharged by about 4 oz.

 

Could the overcharge have caused the expansion valve to plug?

 

Typical expansion valve problems are low side reading low and high side reading low.

I would evac and recharge first see how it is, then change expansion valve.

4 oz is huge amount and is causing the problems.

 

Unlikely

 

ya turns out there is also a blockage in the condesor and a crimped line. will be replace it also on monday.

 

did you do the expansion valve?