Automotive Air Conditioning Information Forum

It has been on R134a for 20 years. That is not the problem. But good point!
I don't know your car's service history (not much, anyway). But if the compressor is the original since the system's conversion to R-134a, and even before that (it could be a GM R4, which isn't known to be the greatest ...

1987 Sunbird, when I switch on the ac button to activate compressor there is immediately a loud screeching sound from the comp area. It stops after about 7-8 seconds. Vents put out ice cold ac. Then, every about 5 minutes the sound comes back, then again, goes away. Could it be the loose ac belt ...

Last night I played with it some more. Connected my brand new 3-port Fieldpiece manifold and all 3 brand new Yellow Jacket Plus II hoses to vacuum. Got down to 370 microns after a few mins. Shut-off pump isolation valve and shut-off pump. Today I'm at ~750 microns, so think I'm OK in regards to ...

A reading of ~500 microns, excellent for MVAC systems, is an extremely small, measured amount of vacuum that you can't even notice on a high-quality Manifold Gauge Set's low-side gauge in Inches of Mercury (InHg). That said, temperature, pressure, and material composition can also affect outgassing ...

Outside of the historical link you provided, I'm unable to help with anything related to the Mark IV (documentation, photos, templates, etc.). However, I do want to acknowledge your posts and wish you all the best with your project.

If your vacuum pump will evacuate the system to about 500 microns, that's all you'll need. Ensure that the vacuum holds.

For an 18-year-old pump that evacuates to 180 microns with an oil change and a direct connection to the micron gauge, that performance is pretty good. Double-check your micron ...

I can see that happening with hose purging. It would be interesting to measure how much is left in the can once it's down to ~25 psi or so.
I'll be using a scale this time.
If you're looking for a refrigerant scale, choose carefully because some professional scales will accommodate a minimum of a ...

John, don't recall a lot of details abt the work done in 2008 other than it was a pain to do in the driveway. I think I used 2 cans. Don't remember abt the oil but it was whatever GM calls for. C5's are a pain to R&R a compressor. Gotta either pull an exh manifold or the water pump or raise the ...

2000 coupe with stock LS1. I had replaced the compressor, condenser, dryer, orfice tube with all GM parts in 2008 shortly after buying the car. Also flushed evap and hoses with special solvent made for that purpose. Lasted until last week. Put abt 100K miles on it during that period
The A/C ...

A few questions: What year is your C5? LS1 (coupe or convertible) or LS6 (coupe) engine? Do you know what the reason was for your V7 compressor failure?