Hello everyone. I have a 1974 roadrunner and am trying to get the ac going. When I got it, it was completely stripped. I have everything now but am having problems. I put a new condensor, new drier, new compressor oil, all new green o-rings in. I have put a vacuum on it each time it's open and it pulls 28 for an hour and will hold it for 24 hours so I know there are no leaks. My first compressor was bad as my high and low side pressures were the same when charged. Now I have a different compressor that seems to be good. I put the correct amount of charge (converted to 134a btw) in it and the low side was pulling a vacuum and the high side was reading 110 psi (when running) and not blowing cold. So last night I drove it to town and on the way back, I kicked the ac on and it was blowing pretty cold, but not quite as cold as it should be. As soon as I got it home, I left the car running and put the gauges on it. It was reading low side of 24 psi and high side of 275. Then when I would pump the throttle, the low pressure would lower and the high pressure would raise. So today I took it out and it wouldn't blow cold again and the low side was reading a vacuum again. Any help would be appreciated.

 

Recover the system and see if the Orfice tube is plugged or resticked.... Also Make sure you did not over charge it.. 22-24 looks good....

 

If it does have a Thermal Expansion Valve your second trip shows that it is not operating smoothly, "sticking open".

 

Thank you for the replies. I know for sure that the correct amount of refrigerant is in it. I don't believe it has an orfice tube since it has an expansion valve, or am I wrong? I will order a new one and put it in and hope for the best. Thanks!

 

I would agree with the bad expansion valve or a blockage....

On the orfice tube.. I was just checking. I have seen folks add them into the system.... But you are correct. OEM did not use them...

 

This sounds to me more like foreign material in the system causing random blockage. You SURE you got all water, dirt, whatever else out of the system?

It IS possible for a TXV to fail intermittent, but that is not the "usual." Usual failure mode of a TXV is for the bulb to lose it's charge in which case it just stays shut