R-134a to R-12
 

Say I have a Denso compressor that has R-134a PAG oil in it.
Now, say I have lots of R-12 and I want to use the 134a compressor
with R-12. my question is... what oil would be best for the compressor
once I dump the PAG that's in it ? ND-oil 6 is what it says on the compressor
This is the OEM denso for my 88.

"have lots of R-12..."


Sell the R-12 at market prices and use the money to buy another Porsche...

Evacuate the system for several hours and use the older mineral oil for R12 compressors.

I replaced the Denso compressor with a new one on my 88 as well. I filled it with R12 (couldn't think of a reason not to). I was told that I could use mineral oil but that the newer ester oils designed for R134 worked fine as well. I purchased a kit from a well known manufacturer and they specifically said use either but we gave you ester oil so when R12 is worth more than a barrell of oil you could always put 134 in. Everything works great.

+1 for ester oil, compatible with R12 and 134

i would use R12 in an R12 system but i dont know if i would convert 134 back to r12.

the problem is the fittings. if you have 134 fittings on the system trying to put r12 in is a real pain.

years ago i had problems with a 134 system when i had a vacuum pump with the old threaded "r12". i could not connect the pump to a set of 134 gauges. i searched a 100mile radius until i found 1 adpater that would convert it.
the threads on the 134 hoses where kind of squared off as where the old style came to a point.

Esther can be used with R12 or R134a.
Esther has the ability to mix with residual R12 mineral oil, while
PAG is not that friendly with mineral oil or Esther oil.

R134a

FWIW, 134 fittings are ACME where as r12 are 1/4 flare.

This is a used Denso off of a 911 that had been converted to 134a. I'll just be using the compressor on my R-12 car. So I need to dump the PAG oil thats in it and add Ester oil.
R-12 mineral oil is very hard to get.

Wax free mineral A/C oil is available at NAPA..part number 209500, about $9 a quart.

yea, saw that, went to my local NAPA... they can order it. I bought some Ester oil there,it's supposed to be compatable with R-12 and from what I've read,the PAG oil in the compressor will have to come out and the Ester will mix better with what PAG oil is left in the compressor...
would like more info on this if anybody knows, Summit has R-12 mineral oil also.

One problem with Ester oil is it is hydroscopic, absorbs water just like brake fluid, PAG does too. A container that has sat around a while could be compromised, sure don't want any extra moisture in an AC system! Best to use R12 mineral oil as it is not hydroscopic. You can find it at any NAPA store for $8-9 a quart.

Perhaps "flush" your compressor with R12 mineral oil to get as much PAG oil out as possible. If the comperssor has been open a long time, the PAG oil has absorbed a lot of water, as PAG is worse at hydroscopic absorbtion than Ester. Also consider using an AC
line flush product from your local FLAPS on the rest of the system. You'll be amazed a how much "black gunk" that comes out!