Automotive Air Conditioning Information Forum

Been a long time since I've done any A/C work... Have a 1985 Avanti (mostly circa 1960's GM stuff with a R4 compressor with high pressure switch and no low pressure switch that I can find). Noted that compressor was not cycling at all (clutch continuously energized) and cooling stopping after full warm-up). Even at start up low pressure gauge was showing "0" pressure and high pressure 115 at 85 degrees ambient After full warm up I shut it down:

Low: 49 psi, High: 125 psi
after 12 hours
Low: 48 psi, High: 70 psi

Since the pressures have not equalized, I'm trying to draw some conclusions if possible. I'm thinking certainly low refrigerant, restriction in low pressure side, leak on high pressure side? Thanks for any feedback.

Have system reclaimed and note weight that was reclaimed. Have system recharged to spec.
To test pressures, have engine at 1800 rpm, windows full open, max cool, max fan, give lo and hi pressures, and report back

This ^^

But I'm also suspicious about the "health" of the R4. To your knowledge, is it the original compressor?

This car used a variety of A/C parts. What does it employ to control evaporator icing?

How many miles has this Avanti clocked?