Oh, and I forgot to mention that it is normal for both the LP and HP to be close to the same when the system is off and that they'll roughly equal the ambient temperature.

Just a thought: It's possible that the system had sealer in it at some point. Sealer can cause all sorts of long-term havoc with a mobile A/C system.

I don't think you mentioned whether it's cooling. But based on your higher than expected LP reading (at an unknown engine RPM and ambient temperature), I'd bet vent temps are rather warm. Since it's impossible to tell from pressures alone whether a system is properly charged, I think I'd start be re...

Yes, looks like a parallel-flow condenser to me, too. Good! Upthread, you mentioned that the HP dropped quite a bit when spraying the condenser with water, suggesting insufficient airflow across the condenser. Since you installed a new electric fan and we assume that it's working as it should, doubl...

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...