AC Repair 81 C10

I would like help and direction. Totally newbie to AC. Trying my hand at repairing my trucks original AC. New to me about 6 months ago.

Did not have a V belt around compressor or electrical hooked to it. Found the electrical off the switch. Hooked it up and grounded the compressor. Put a new belt on it. Jumped switch. With engine running and turning on AC, compressor engages and seems fine. No strange noises. Has a Murray R4 compressor.

Next I just received a gauge set and vacuum pump. It doesn’t have any Freon in it. I vacuumed it down to -30 for 30 mins. Closed manifold gauges. Turned off pump. Has held vacuum now for 2 hours without needles moving.

Thinking it was original fittings on the lines for R12 I bought adapters for QD’s. When I went to install adapters I found the drier and high side line already had crimped QD’s on them. Not after market screw on ones. Maybe already converted to R134? Owner passed away so no history or stickers anywhere to note this. I had also unscrewed the pressure switch being nosy and it had a green O Ring on it.

So what should I do next ?

I have ordered a drier and orifice just in case.

A. Change them and fill it with R134?

B. Change above parts, replace compressor or at least drain and refill it with oil. Then charge it? What type oil?

D. All the above with a complete flush and use what type oil? Easter or Pag150?

Attempting to do this as cheap as possible but as well as possible too. Thanks for your time and input.

If the system was retrofitted properly there will be a sticker indicating oil type, refrigerant type and capacity. Replace the accumulator and orifice tube (don’t force it, otherwise leave it in there), Drain and fill compressor with Ester oil if no sticker indicating that it has already been done. Good luck!
P.S recommend 75-85% charge of the recommended R12 charge. Or…..if you can find some NOS R12, that would be highly recommended. That is what I am running in mine.

Just pulled the orifice. Any take away besides it needs a full flush? Compressor?

Bought a compressor and condenser.

Ouch. Thats what I expect mine to looking like when I get the point of working on the AC. You (and myself as well) are probably in for a new acccumulator/drier as well.....

The system will need to be flushed thoroughly before installing new components and recharging.

Here's a video from the Repair Geek that goes through the steps --> VIDEO_LINK

Balancing "getting it right" with "as cheap as possible" may be a bit of a challenge. The R4 compressors (new and reman) do not have a stellar reputation for longevity. The cost to put a Sanden style compressor on it may not be too much more and will be a big step up in terms of efficiency and longevity.

Here's an option on the compressor at $244 and brackets at $131.

Good luck. Post back with questions and status.