I'm trying to understand what the problem is, but I'm a bit confused about your comments concerning pressures, among other things. So, yes, I agree with Cusser. Start by having a professional A/C shop diagnose it. They'll have the training, experience, and specialized equipment necessary to make the...

I agree with Cusser. Your system was designed to work with R12. Converting to R134a is always somewhat of a compromise. I wondered, too, whether you replaced the original tube-and-fin condenser with a more efficient parallel-flow condenser. If not, doing so might help it cool a little better with R1...

I wonder about the oil. If the rebuilt compressor was empty of oil and you added 8 ounces of PAG 150, that sounds about right. But if the compressor already had oil in it and you added 8 ounces more, obviously that would've been way too much. Just a thought.

Since we don't know what the pressures are, I wonder if by 'zero' the shop meant that they were very low. Hard to tell from across the pond. But if that was the case, I would begin by recovering whatever refrigerant might still be in there, then evacuate and recharge with the correct amount of R134a...

Vehicle year, make, model, and engine size will help us help you to diagnose this.
Question: Since you took it back to the shop and their machine showed 'zero,' does the compressor run anymore?

I readily admit to learning something new. Right after you said that, I went out to examine the alternator on my 2018 Toyota SUV. Unfortunately, the alternator is buried so deeply that I wasn't able to determine whether it has the type of pulley you mention. The vehicle does use R134a and not R1234y...

To my knowledge, there is no clutch on the alternator, just a pulley bolted directly onto the shaft and driven by the serpentine belt. I don't think your variable-displacement compressor has a clutch, either. So whenever the engine runs, so do the alternator and compressor. Instead of starting and s...

If you have only about 12 ounces in it (one can), it is way too low. And as Cusser alluded to, the compressor won't engage.

I would approach this by first recovering the refrigerant that's in it now, pulling a good vacuum for at least 30 minutes, and weighing-in the factory-specified charge of 19.0 ounces of R134a. Then take LP and HP gauge readings at an engine speed of 1,800 RPM with the A/C system on and report the pr...

I have a few additional thoughts. If you saw frost on the evaporator box cover plate while charging, that would indicate to me that the evaporator has a large leak. So I agree with bohica2xo on that. Sometimes, debris like leaves will accumulate in the box and over time, cause corrosion and eventual...