[AG]

Resurrecting an R12 system that was previously functional. Going with a Sandan compressor, new hoses, drier, condenser and not sure about the POA valve yet. Any recommendations about where to source parts or what to do with the POA valve? I think I can readjust the POA for 134a or get a cycling one but not sure.

[Squidward]

Flush every component. The mineral oil is not compatible with r134.

If you are using a Sanden, you might consider doing a POA eliminator kit so it becomes a ccot system. Poa systems are frosty, but I don't think a poa would be a good fit unless using an oversized compressor like an A6.

You are correct, POA valves can be adjusted for r134 pressure, and a 134 spec expansion valve could be used.

New hoses should be used, especially for 134. The old hose has a molecular porosity not good for 134. Orings need to be the green ones. Ester oil can be used for either r12 or r134. Pag oil is only for 134. Mineral oil is only for r12.

The part about original systems that scares me most is the controls and vacuum diaphragms.

[AG]

Thanks for the advice. The good thing is the system was working and the diaphragm on the firewall was replaced with a new one.

[srmmmm]

The R134a expansion valve conversions work fine. If you're not concerned with "period correct" on the condenser, try to source a micro-tube parallel flow condenser. They have a much higher mass to refrigerant ratio for the best heat transfer, especially beneficial in R134a systems. I already had a new serpentine condenser in place when the R134a compressor was installed, and the A/C is acceptable, but not outstanding.

I spent 12 years in the HVAC industry doing systems for Mazda, Subaru, Isuzu, Saturn, Volvo and BMW through the transition from R12 to R134a.

[rolling money pits]

Originally Posted by srmmmm

The R134a expansion valve conversions work fine. If you're not concerned with "period correct" on the condenser, try to source a micro-tube parallel flow condenser. They have a much higher mass to refrigerant ratio for the best heat transfer, especially beneficial in R134a systems. I already had a new serpentine condenser in place when the R134a compressor was installed, and the A/C is acceptable, but not outstanding.

I spent 12 years in the HVAC industry doing systems for Mazda, Subaru, Isuzu, Saturn, Volvo and BMW through the transition from R12 to R134a.

Was coming in to say something similar…
Long time ago, when was in the jobber aftermarket, I seem to recall 134 conversations necessitated a change in hardware due to it being less “potent” than R12, but couldn’t recall what it was, evap or condenser.

[AG]

Any recommendations for part sources?

[Tim Corcoran]

This may be too late but, the Pro6ten compressor is a much better compressor and is a direct bot in going from the factory A6 compressor. Plus it makes it a simple job. Another suggestion is to install a new parallel flow condenser also more efficient.