Automotive Air Conditioning Information Forum

I have a 69 Camaro that I recently purchased. The POA valve had a r134 connector screwed into the old r12 low side port and the hose that should have had a high side port didn't. I assume this means it was converted to r134.

I noticed a small oil leak in front of the compressor but nevertheless the car was blowing some cold air. This weekend that stopped.

I assumed that the car was converted to 134 and tried adding some to see if I could get it cold. Didn't really work. It might have been because the r134 to r12 adaptor was bad.

I then decided to pull a vacuum and see if it would hold while at the same time putting the correct high dude hose on.

It hold a vacuum for a few hours and then went to zero. Not sure if it's the compressor, my new hose, or something else.

I figured since I've gone this far I should get the compressor rebuilt.

So here's my question: how do I tell what type of oil is in the system? I will need to add it to the compressor. That is, is there a way to tell the difference between PAG, ester, or POE?

Thanks!
Ed

Emdoller wrote:So here's my question: how do I tell what type of oil is in the system? That is, is there a way to tell the difference between PAG, ester, or POE?

An analytical chemist (like me before I retired) could use FTIR to determine easily the oil type by comparing to standards. I did that with a few new or rebuilt compressors to determine whether PAG or R-12 type mineral oil had been added. There may be other ways, do a Google Search.

FTIR is Fourier Transform Infra-Red spectroscopy

I tried google. Can't seem to find anything.

Cusser wrote:An analytical chemist (like me before I retired) could use FTIR to determine easily the oil type by comparing to standards. I did that with a few new or rebuilt compressors to determine whether PAG or R-12 type mineral oil had been added. There may be other ways, do a Google Search.

FTIR is Fourier Transform Infra-Red spectroscopy

Yeah, we all have one in our garage!

Assume the worst with a sloppy half-way conversion. It probably has a double dose of oil, and a dessicant that is not compatible with 134a.

You need to break the system down and flush the evaporator & condenser back to bare metal.

The POA valve needs to be calibrated for 134a,or you need to stay with R12.

Probably best to pressurize the system with a few ounces of 134a & finds the leaks before you tear it down.

Thanks. I was thinking the same thing as I doubt the POA was calibrated. I've never flushed a system... How hard is that to do?

Ed