mepoling Posted July 11, 2004 Report Share Posted July 11, 2004 My 1996 Seville Air Conditioner stopped cooling (at least sopped cooling well, vent temperature around 60), today. I checked the the Low Pressure, and it was around 130psi at idle, and would drop to 110 psi at 1800 RPM. I added 24 oz of R134. The low pressure reading is now about 70psi at 1800 rpm, cooling still ineffective. As an interesting observation, the compressor engages when I first turn on the A/C after starting the car, but does not appear to disenguage when I turn off the A/C (until I turn off the car and restart). Cycling between A/C and Vent (A/C off) seems to have no effect on the vent temperature. I have not noticed any symptoms of a compressor problem (no noise), and have not had any other problems with the air conditioning. No DTC / Fault Codes. The evaporator gets cold (cool) and the high pressure line gets hot. The car did sit for approximately 3 weeks. Any thoughts / suggestions? Link to comment Share on other sites More sharing options...
Scotty Posted July 11, 2004 Report Share Posted July 11, 2004 If I am not mistaken, the MAX pressure that you should have on the LOW PRESSURE side is 44 and that is MAX. Are you sure you are reading the LOW PRESSURE side, ie the side where you put the R134 in? 24oz is quite a lot of R134 and that could be the reason you have such a high reading. My ADD REFRIGERANT message was on and I was able to bring it up to normal with 2-8oz cans. Let us know what you find out, Mike Link to comment Share on other sites More sharing options...
mepoling Posted July 11, 2004 Author Report Share Posted July 11, 2004 Yes, quite sure that I was reading the low pressure port. The fitting on the high pressure port is also larger (my guage will not fit it). I agree that 24oz is a lot, but the pressure was higher before I added any freon (adding freon dropped the pressure from 110psi to 70 psi at 1800 rpm). I have read a little about "reed valves" and "coolant control valves" in the compressor causing some similar charateristics (high pressure at the low pressure port). But, I have also read the low freon causes smilar syptoms (maybe excess freon as well?). With all the (often annoying) diagnostics built into the Seville, I am very surprised to actually have functional defect without some fault code. I am a little concerned about taking the probelm to a mechanic prior to getting educated a little more. I would not like to dump $800 on a compressor if the problem is much simpler. Link to comment Share on other sites More sharing options...
Scotty Posted July 12, 2004 Report Share Posted July 12, 2004 The system will set a code and disable the system if the pressure is too low to save the system from damage however it will not set a code if the pressure is too high. I am miffed as to how your pressure could decrease by adding freon. It sounds like you have too much freon anyway you look at it. Maybe your system is FROZEN bound. How are you checking the pressure, a gauge set or a guage that looks much like a tire guage? If you are at 70 pounds I do believe you have too much freon. By the way, did you add any oil? Too much oil can cause troubles also. You might save yourself a LOT of problems by having the system evacuated and recharged, many radiator shops specialize in AC systems also. Mike BTW the reason I love the Cadillac is because of the computer diagnostics... Link to comment Share on other sites More sharing options...
JohnnyG Posted July 12, 2004 Report Share Posted July 12, 2004 I am no expert in this field, but I have heard of this happening. I think it was caused by a plugged filter/water absorber just before the condenser. If the pressures are high, I would suspect that the compressor is, well, compressing. It's just that the freon has no where to go to expand, or can't expand quickly enough. I've heard of weak cooling cased by a plugged expansion orfice screen as well, but that one is just before the evaporator. That would cause abnormally high HIGH SIDE pressures...........now adding freon to correct either of these problems might cause all sorts of weird pressure readings. Never underestimate the amount of a persons greed. Link to comment Share on other sites More sharing options...
franey Posted July 12, 2004 Report Share Posted July 12, 2004 IF you do not have a set of gauges borrow one , those that come with a can of do it yourself freon , are sometimes way off. Some people have thought they had a problem when in reality it was a bad reading. IT is much easier too diagnose once you are comfortable with the reading. Link to comment Share on other sites More sharing options...
KHE Posted July 12, 2004 Report Share Posted July 12, 2004 You need to obtain the high and low pressure readings when the compressor is engaged in order to diagnose the problem. Rent/borrow/buy a set of gages. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
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