'96 PA A/C Acting Weird

[HotZ28]

Originally Posted by Smitty's Buick

HotZ28 - Thanks for the quick reply! Is there a way to test the diode?

Yes, Click Here

[Smitty's Buick]

Any idea where exactly the diode is? I traced the wires back from the compressor into the black tubing. I'd like to know roughly where it is at before I go tearing all of the wires out further. Thanks.
Smitty's Buick

[HotZ28]

The diode should be taped slightly above & into the 2-wire terminal that plugs into the compressor.

[Smitty's Buick]

Well, I never did find the diode, but I think I've got it fixed!

Given the fact that there was only 10V at the compressor connection, I decided to inspect the battery cable going to the fuse block. The cable was quite stiff, so I replaced it. The voltage at the compressor jumped to 13.8V. Much better. The voltage at the battery jumped from 13.6V to 14.2V. Much better.

The compressor still did not kick in. I checked continuity across the back of the connector pins and had none. That was another problem. By bending the pins at the compressor connection so that they would engage "harder" into the connector, resulting in good continuity, the compressor clutch engaged and ran normally.

Glad to finally have this behind me (hopefully). Just goes to show that you need to look at everything and pay attention to the symptoms. Hopefully this post will help someone else down the road...

Smitty's Buick

[Smitty's Buick]

Well, I am not real sure what to think any more.

The AC has been running great until last night. The same issue has returned. There is 12.5V at the compressor but the clutch won't engage.

Hot wired the compressor directly to the battery and it works great. Checked continuity across the compressor at the connector and across the connector with no issues.

Is there something going on with the clutch or am I missing something else?

Smitty's Buick

[HotZ28]

When you "Hot wired" the compressor, you are bypassing the pressure switch and other sensors that are used to command the clutch to engage. What are the high/low side pressure when you force the clutch to engage? You may now be low on refrigerant.

[Smitty's Buick]

This keeps getting stranger and stranger, but I'm sure there is a logical explanation. The AC worked great today! This morning, to and from lunch, and then home. Ran around town tonight... nothing.

I got a pressure gauge for the low side and checked the pressure. The gauge pegged past 100 PSI. Looking at the R134a P-T chart, 100 PSI translates to ~87*F. I'm sure it was hotter than that under the hood. I plan to check it in the morning when it's cooler and maybe hot wire the compressor again and see where the pressure winds up.

I'm guessing that checking the low side pressure with it running will tell much more than the static pressure.

Smitty's Buick

[Smitty's Buick]

So, the daily update - checked the pressure this morning. 62*F outside, and about 60 PSI, which is about right. Started the car, the A/C kicked in, and showed about 25 PSI, just at the bottom of the "green zone" on the gauge face.

HotZ28 - You are right again! I think I will add a can to verify that I've got all of the other junk fixed. That should last the rest of the season (still calling for 90's next week), then I can have the system leak checked and maybe fixed next spring.

Smitty's Buick