Correct PSI for R12 AC system
 

WHat is the correct reading for the low pressure line on our R12 AC system?

The Technical Data section of the shop manual lists -

Low pressure - 21-43 psi
High pressure - 185-213 psi

Also, refrigerant amount is 21.2 ounces, and compressor oil amount is 3.7-8.5 oz.

That help? :)

Dale

WOW. My low pressure line is at 113 psi!!!!

Can I just vent it out? I know technically you are not allowed to, but what I mean is, will it hurt the car in any way?

Do you test it while the car is running, or off? There must be something wrong, no way I could be that overcharged.

You're sure you're on the low side? The low side is the big pipe, the high side is the small pipe.

If you have VERY high pressure, you've probably got a plugged expansion valve or some other major system problem.

BTW, section G in the back of the shop manual has all the troubleshooting stuff. I've got it right here in front of me - if you can get readings for both the low and high side, I can look up the troubleshooting for it.

Dale

Yes, definately the low side. I'll go outside and get readings, do I do it running or off?

If the pressure is really that high, the compressor shouldn't engage. But, the shop manual says -

- Turn AC fan to full speed (4)
- Set temp at coldest setting
- Bring RPM's to 2000

If the compressor won't engage, just test without - doesn't matter if the engine is running or not.

Dale

Strange, this time it was 43 psi on the low side! Must have to do with the car running. Couldn't get the guage on the high side, to far down in there for my guage. But I gues everything is ok if the low side is 43, right? Or is that too close to the high end?

Yeah, that is a bit high. I'd try and remove what you need to to get a high side reading - that would give lots of answers, especially if the expansion valve is plugged.

How well or not well does the AC work on the car?

Dale

It works pretty good, but just not on real hot days like 95 + degrees. And it cycles on and off a lot. That is what made me really start thinking maybe something was wrong, the cycling on and off. It does that like every 5-8 sec on real hot days.

the readings are taken with the car on the ac running. 43 is ok the pressure is variable depending on outside temps. what was the high side at like 2500 rpms? low side?