Hello, I have problems with my air conditioner. The car is a 1988 Olds Custom Cruiser with the most basic air conditioning. So there are no electronics installed, just a low pressure cycling switch that is supposed to shut off the magnetic clutch of the A/C compressor when the low side pressure drops below 22 psi. This used to work properly as well. Now the old R4 compressor was defective (no more power and leaking, after 4 years of operation). I then replaced it with a new compressor from ACDelco (GM 15-20206). Its behavior is strange: the magnetic clutch turns on, the low pressure is about 40-44 psi, the high pressure is 190 psi, and this regardless of the speed. As a result, the magnetic coupling does not cycle either. A cooling effect is detectable, at an outside temperature of 30°C I was able to measure just under 9°C at the air outlet nozzle on the driver's side, at the center nozzle it has always been more, something like 13°C. There are two possibilities now: 1. the new compressor has a flow control device internally, so it no longer needs to cycle. 2. the new compressor is broken. Does anyone have experience with these compressors? Thank you very much for your answers. Best regards Munzel
Luckily, I can work with degrees C as well as F; with air conditioning, you want an 18-21° degree drop from ambient. To achieve this, you have to make the system work hard, on RECIRC or MAX, with all doors and tailgate open. If it can achieve a 21 degree drop with all that, then your A/C is at peak efficiency. If I remember correctly, the compressor you have has a variable swash plate to control the pistons, so cycling is not necessary.
I'll just add a question of what refrigerant are you using? 22psi for low was for R12 with a high around 165ish. R134a operates closer to 35psi low and 175-180 high. Cycling on these compressors was nowhere near what newer cars are expected to do. They may cycle when it isn't overly hot out, but when it's warm (and 30C is considered "warm") it should run close to all the time. The absolute coldest you can really ever get out of one of these systems on recirculate full blast is 4C (39F) for an old-school R12 A6 compressor, I get closer to 7C (45F) with more modern gear. This also presumes you have an efficient condenser and fan assembly to rip heat out as fast as you can. I have never liked these R4 compressors and consider them to be inferior to the A6 they replaced and the H4 or whatever that came after. Personally it sounds like the system is working just fine, if a little on the lesser efficient side. I would check your ducting inside the car and the evaporator box for dirt and trash obstructing air flow and your radiator\condenser for air flow as well.
Hello, thank you for your answers. The system is filled with R134a (R12 is banned in Germany). Actually the air conditioner worked fine for years. It cycled as expected, only when idling at very high temperatures (95°F) the compressor remained permanently in operation. This is what I had expected. There was also definitely a dependence on RPM: at higher RPMs, the low pressure dropped faster to the cutoff point (21 psi). http://www.e38.org/pparish/gm-rp.htm But now nothing like that happens, the low pressure stays constant at 40-44psi, no matter what engine speed. Condenser and evaporator are also clean (I straightened all deformed fins of the condenser). That's the compressor: https://www.rockauto.com/de/moreinfo.php?pk=83171&cc=1421626&pt=6628&jsn=453 I somehow can't imagine that there is a swash plate in it for power regulation. I wrote to ACDelco to find it out. They referred me to go to a local Service center. But ACDelco has no service center in Germany ... As I said, the overall cooling performance is satisfactory, although not as good as with R12. I just don't want to drive around with a faulty A/C compressor, which then brings metal debris back into my system. R134a has also become quite expensive in the meantime. Next time the A/C fails, I may use a similar refrigerant to the Australian Hychill -30. This is supposed to be really good: cheap, environmentally friendly, smaller charge, good cooling. But -not approved. If I receive an answer from the manufacturer of the compressor, I will write it here. Best regards Munzel
Well, if it worked fine before and had lower pressure but now doesn't, ASSuming it isn't a bad compressor, that's usually a sign of either not enough airflow through the condenser OR too much refrigerant in the system. The airflow is an easy check, the refrigerant is less so unless you are the one who personally did the system. Although I could easily imagine a newer shop over there that isn't familiar with the R12 vs R134a conversions would put in too much refrigerant if they were going solely off of the spec from the factory for 1988.
I was present during the filling of the system. The original amount of R12 was 1.5kg, now there is 1.2kg R134a in it. So there is no error occurred. This is all somehow strange.
When the compressor was replaced, was the orifice tube also replaced? It acts as both a control valve and metal filter.
Yes, the orifice tube has also been replaced. My first thought was that this could be destroyed. Lack of cycling is also mentioned by the Car Shop Manual as an indication of a broken orifice tube.
Update: the manufacturer has not felt obliged to respond in any helpful way. My thought is that there may be a defect in the dryer that is preventing the refrigerant from flowing freely. I will replace the dryer in the winter.
I had the dryer replaced these days. Now the system seems to work correctly, the compressor cycles again. So the flow of refrigerant through the dryer was restricted. Now I am curious how long the system will work error-free this time. After all, it is now compressor No. 4 ... If the cooling capacity is too strong in summer, I will change the cut-off pressure a bit more to save the compressor.
Ugh, Same year here, but a Buick Electra Estate Wagon. My A/C is automatic with the touch pad. I think it's due for service, and its the first repair I'm not really looking forward to.
Luckily, the basic performance procedure itself is straightforward, and just doing that should only be an hour's time, if the system is full and pressures are where they need to be. Sometimes, adding 'just a bit' of refrigerant to get peak performance can be a part of that hour's labor. What I would be concerned about are the electronic A/C controls; that's a separate animal. If an electronic problem is discovered, that typically can take 1-3 hours diagnostic time. But, when it's time for the check, let us know how it goes.
