I put my 87 engine in my 86 and then I converted it over to R134a. It blows ice cold but only if I rev the engine up to about 4K rpm to get it started. It runs perfectly for about 10 minutes then it slips into blowing ambient air. If I re-rev the engine, it comes right back to life blowing ice cold. According to the link above, my problem is with the compressor switches.
Can anyone confirm that the switches in the compressor are the likely cause and cure? I have replaced the front pressure switch and also the connector that is wrapped in heat tape that plugs into the compressor by the pulley.
I found the part numbers for the switches that I need in this thread:
I only used the gauges while pulling a vacuum on the system to check for leaks. I had the system filled at a shop that I trust. I wouldn't know how to troubleshoot this problem.
Been searching the net. Many people have a problem with warm air while sitting still and it is speculated that the cause is a faulty fan or condenser blockage. I have neither those problems or conditions. My AC will blow ice cold whether parked or running down the interstate once it kicks in. Whenever I notice that it is blowing warmer, I simply shift to neutral and rev it up then shift back to drive ( or stay in Park ) and it comes back instantly. It always lasts for a while before going warm again.
It seems to work longer on Max Hi than on Max Lo. Then again, I always start on Hi then scale it down as it gets too freaking cold to stand it. Perhaps by the time I'm switching the fan to a lower speed, it is about to stop anyway.
I don't think the system is freezing up because it will re-start instantly as soon as I rev. There have been no exceptions to this.
I read someone else found a bunch of dirt built up around his clutch. He thought it might be making it difficult for the electromagnet to pull the clutch in. After he manually pushed the clutch in with a screwdriver a few times, he blew the debris away with compressed air. His started working correctly after that. I'll check for that today and see what happens. This may be a good periodic maintenance procedure that everyone should do to keep their compressors working as long as possible.
Just a guess, but one of those switches is there to turn on the fan when AC is on. If you have no air flowing over thr rad, like when sitting still, then the AC will not work well. But checking the pressures with gauges will help to diagnose this also.
Hook up a set of gauges and see what's going on. Could also be the air gap is too wide on the clutch. Gauges would be faster/easier to check first and rule out other issues. Check pressures when car is off, car is on, and while AC is running. See what pressure the low side is at when it kicks on and kicks off. Also note the ambient temperature while doing it.
The fan will run if the AC is on. 1 switch is a backup to turn the fan on, and the other turns the AC off if pressure gets too high in the system.
Hook up a set of gauges and see what's going on. Could also be the air gap is too wide on the clutch. Gauges would be faster/easier to check first and rule out other issues. Check pressures when car is off, car is on, and while AC is running. See what pressure the low side is at when it kicks on and kicks off. Also note the ambient temperature while doing it.
The fan will run if the AC is on. 1 switch is a backup to turn the fan on, and the other turns the AC off if pressure gets too high in the system.
Thanks, Can I change the compressor switches or adjust the air gap without losing my R134a?
I messed with the clutch a little bit, pushing it in and rotating it making sure it was free to operate as smoothly as possible. I started the car up and the AC came on immediately with no prodding from the accelerator. I then watched it for a while and I saw it cycle off and back on. This was at idle in Park up on jack stands. I don't know if it has ever cycled back on by itself since being installed. I hope this is a solved problem. I'll take the car out tomorrow and drive it around to give it a proper test.
Thanks! The guy in the video seemed like he was just trying to get the clutch as tight as possible without binding it up. Is that an acceptable way to do it? If not, would you use a flat feeler gauge to measure that gap?
I did a short driving test and the compressor seems to be cycling on and off without any prodding by me. I'll drive it to work Monday or Tuesday to give it a more thorough test. Although it is coming back on by itself now, it does seem to take longer that it should.
Just how long should the compressor be 'OFF' during a cycle?
That's a hugely loaded question. Several things will be a factor like ambient air temp, ability of the coolant fan/condenser to cool the freon, current freon charge, engine rpm etc. The cycling is based on low side system pressure which goes down as the compressor is turning and goes back up as the compressor is stopped. The idea is to maintain an average system pressure that gives near freezing outlet air temperature. The compressor cycling switch (found on the accumulater/dryer in our cars) can go bad over time. It also has different pressure settings for r-12 vs r-134a. It is possible that yours is not correct or is faulty. I had one go bad and it appeared to be working but not at the right pressures and it was intermittent in operation. I changed it and all was well. Your issue could be something else though. Not enough info to diagnose.
I replaced the cycle switch when I did the changeover. I'd say it is working correctly. That was the first time I had ever watched an AC compressor clutch so what do I know.
Drove it to work today. AC still doing the same thing. I stopped by O'Reilly and borrowed the AC clutch kit. That temporarily set me back $120! Going to drive the mustang to work tomorrow so the Fiero will be cool to work on when I get home.
Well mine was way off. My largest gauge was 0.030 and it went in easily. I was worried about putting it on too right or breaking something so I tightened it down to around 0.025.
Gonna do another test run to work tomorrow. If it isn't working better, I might try to tighten it some more.
After several successful short trips, I finally got to test the AC on a trip over an hour long. It worked flawlessly. It wasn't that hot outside but it was warm enough to use the AC the whole time. Daily temps have only been in the 70's so I'm waiting for a really hot day to try it. So far so good!
