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1970 Air Conditioning


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On my 1970 Monte Carlo the air conditioning blows very cold, but every so often it cuts out for a short time then comes back on (not even long enough to let the inside of the car warm up) The refrigerant is full. I replaced the clutch cycling switch in the low line and made sure it was getting 12V. The camshaft won't allow the engine to idle when when the air is on, so I installed a dash pot to raise the idle speed when the ac is on and that works good. I wired it into the + lead going to the compressor. When the ac cuts out that dash pot also has no power which means the power to the compressor cuts out. These intervals are very short. Does anybody know if the ac system has a thermostat to cycle on and off?  Thanks

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  • jft69z changed the title to 1970 Air Conditioning

TTT     I dont have an answer for you Wayne, but its going to the top again. I know the boards are very light this time of year, just bear with them for a while. Someone will get back to you just might take a little time.🙂

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You need to take it to someone who works on auto AC units and get them to hook up some gages to check the readings.  It is possible the switch is working properly.  If I am not mistaken, it is supposed to cycle the compressor rather than the compressor running all the time.  It is possible the system is overfilled also.

When I redid my AC the POA came with an inline switch like I think you are talking about.  My 70 had the original POA when I started the rebuild of the AC system and the original did not have this switch.  When I asked the company I purchased everything from about the switch on the POA they explained to me that it is designed to cycle the compressor rather than it running all the time.  It is possible the switch you are referring to is working properly and if it doesn't cut off the compressor long enough for the inside to get warm it sounds like it is working properly.

Again, I would suggest you take it to someone who works on the systems for a living.

rob

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Wayne, did you or someone change the ac system to R134?? When I got my car the prior owner said he changed the system to R134 so I thought it was all good. The air wasn't really working so I took it to my mechanic and he said the original POA valve wouldn't work and that the system had to much freon. He also replaced the expansion valve. I hope that helps, good luck

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Thanks for the input. I get a little frustrated when I am trying to figure things out. Yes the system is converted over to R134. Eventually I will take it to an AC place. Maybe it is working properly, because the car never gets too warm.

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 there should be a temp sensor in by the evaporator to sense the temp so the evaporator doesn't freeze up. Once it does hit the temp threshold it should turn the compressor off so it doesn't freeze up to a block of ice  and send liquid refrigerant to the compressor. Pretty sure they call it a freeze switch 

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