Ducman82

Odd being they have no idea what oil you have in your system, and mixing is a no no

The Forgotten On

You can mix ester oils, just not PAG. Otherwise you will have a sludgy mess that will destroy the compressor.

As usual, do a chemical flush of all of the lines first to remove any lingering oils from the previous charge.

WallyP

The reason for using POE oil is that it will tolerate small amounts of residual mineral oil.

PAG is a better oil, but will not tolerate any residual mineral oil. R-134a does not play well with mineral oil.

bureau13

I didn't think it was so odd, given that I requested a compressor for R12. So Roger knew what type of system it was going into, at least. I don't know if they would have given him one with POE or PAG oil had I said R134a, or one that was empty.

drooman

The only way to be sure about oil types/quantities is to flush out the entire system with AC flush..every line and component. Then drain AND hand pump the new/ reman compressor as dry as you can (you'll get most of it out) then oil charge the system with the correct quantity of oil. Most compressor re-fits and 134a conversions I've torn into have too much oil built up in them from various compressor swaps over the years...too much oil means higher vent temps, and too little means a short compressor life.

griffiths

Most of the 'oil' issues are a result of poor or lacking service documentation, especially when a vehicle has gone through numerous owner's and service facilities. +1 on the 'if in doubt, flush it'.

When a vehicle is converted to R134a a blue R134a conversion sticker should be placed near the service area (engine compartment) which details the type of oil used, and the work/repair order should be noted as well (ie. amount and type of oil, amount of refrigerant). However, many techs and DIY's are either not familiar with this or simply fail to do it.

For the past 20 years of providing R134a conversion kits and systems we have always provided the requisite R134a conversion label and note in the procedural instructions to document everything: evacuation process, oil type and amount, refrigerant amount, pressures and temperatures. Having that data comes in very handy while troubleshooting system issues.