Hey all. My 1990 civic hatchback had working AC all last summer, and now it is not working for this summer. It's been converted to R134 and all O-rings were replaced last year. The problem I am having now is that I can charge the system and it will hold pressure just fine. However, once it gets to the proper amount of pressure to kick on the compressor, the gauge instantly goes to 0 psi the second the compressor comes on. I pulled out the valve on the back of the compressor and it seemed fine. Put a bolt in there for the heck of it just to eliminate it from the equasion and the car is still doing the same thing. What else could be bad that is causing this?? I put UV dye in the system and it is not coming out anywhere in the engine bay that I can see with the black light. There was a ton of dye at the back of the comressor, but if the valve is plugged, where can it be coming from?? I'm sort of new to AC systems so any help is much appreciated.

 

What side, [low or high] goes to 0 PSI?
What happens to the other side PSI?

Problems with A/C when a leak is not the problem and compressor is good is almost always the expansion valve, and not that uncommon on older cars.


Questions.

What are you putting into the system, [refrigerant] exactly, [brand name]?
How are you putting it in?
Are you using a proper A/C manifold gauge set?
Do you have a vacuum pump? 94

 

Low side goes to 0psi when compressor is engaged. Not sure what happens to the high side because I am going off a cheap autozone gauge that only plugs into the low side port.

I am trying to put in an off the shelf can of R134 from advance auto. Heres the exact product...



I'm adding it per the instructions, through the low side port with AC on full blast and rotating the can between the 12 o'clock and 3 o'clock positions.

Gauge set is just the cheapy one that comes with the kit.

And no, I do not have a vacuum pump.

Last summer, when my AC was working, the compressor made a rattling noise while engaged. I looked at it when it kicked on recently and the clutch was spinning with the compressor pulley, so I know it's at least working. May need a replacement soon though.

 

OK, better then RedTeK or Duracool, [and a lot of others] as it actually has R134a refrigerant in it, unfortunately it also contains sealers and they can be a problem.

I can think of two things that will cause the low side pressure to go to 0 when compressor turns on, a low refrigerant charge or a restriction, [re sealers].

My guess is the expansion valve is stuck almost closed, [can be caused by sealants in DIY A/C charge systems]. 94

 

Well thanks a bunch for the info! The expansion valve is one of the few things I didn't actually check since you have to dig open the dash, but now I will be sure to go in there. They are not very expensive either to replace from what I've seen. Last summer, I did throw a full can of leak sealer into the system so it may have very well gummed it up. I always hate using things like that but it seemed so easy at the time... Doh!

Anyways, thanks for the tips. I'll check it out further and post my results.