1G Converting R12 to R134a refrigerant & oil

[AWD-Tony]

I’m converting from R12 to R134a. For R12, our cars take 33oz of R12 & 5oz of mineral oil. Now that I’ll be converting to R134a, what’s the correct capacity?

I’ve read a few threads on this topic and I only found a single post saying you can’t use 33oz of R134a.

So...
How much R134a? Is mineral oil compatible with R134a?
If so, I guess that amount won’t change. If not compatible, what oil and how much?

Thanks
Tony

 

[Dericsh]

It’s been a while but I believe you want to put about 80-85% of the original capacity then top it off if needed.

You want to look for POE oil, it’s compatible with both types.

 

[TerminalTalon]

75-80% capacity but watching the low and high side gauges is key for AC stuff.

 

[AWD-Tony]

There was some oil in the evaporator. Can all the oil be removed when evacuating the system?

 

[1990TSIAWDTALON]

O'Riellys sells a citrus type of cleaner that I used on my Chevy Caprice when I flushed it and put all new stuff on her for nice cold A/C.
@Jk's97DSM is correct in watch the low side and high side on the manifold (Do you have a set of gauges Tony?).
Also, you can still find R12, and it is a colder refrigerant than R134 is.

I do my own A/C on all of our cars, so keep the low side pressure to 40 lbs or so and the high side no more than 350.
That is what I try to do and usually works out well.
Marty

 

[AWD-Tony]

O'Riellys sells a citrus type of cleaner that I used on my Chevy Caprice when I flushed it and put all new stuff on her for nice cold A/C.
@Jk's97DSM is correct in watch the low side and high side on the manifold (Do you have a set of gauges Tony?).
Also, you can still find R12, and it is a colder refrigerant than R134 is.

I do my own A/C on all of our cars, so keep the low side pressure to 40 lbs or so and the high side no more than 350.
That is what I try to do and usually works out well.
Marty

Most likely not but I did see a set of gauges and vacuum pump locally for $100, so I might pick it up just to have it. This way I’ll know if there’s any leaks even if I don’t charge it myself.

Only oil was in the evaporator so I’ll pull that out AGAIN and flush it out. I know R12 is colder but seems to be harder to find. I read somewhere that you can’t buy it anymore unless you have a license and it’s not cheap so I’m just going with the retrofit

 

[1990TSIAWDTALON]

I use a Gauge Set like this (yep its cheap but it works good) and a Venturi type vacuum pump that runs on my air compressor exactly like this.

I have lots of "friends" that want me to "tune up" their A/C, so this is what I use.
Just putting it out there.

 

[steve]

@AWD-Tony Do you remember how this turned out and what you had to do?

 

[LaserRS92]

@AWD-Tony Do you remember how this turned out and what you had to do?

Looks like he hasn't been on since November of '23. I've been wondering what happened to him. I bought some parts off of him in person years ago and he was very happy to chat about our projects and different ideas. Cool dude, hope he's okay.

 

[CrackedDSM]

Just as an fyi I am actively doing this conversion. Once I solve the slow leak I’ll update this thread with what I used as far as ounces of R134a, and oil.

So far I’ve used Ester Oil w/ UV dye because it’s compatible with mineral oil and PAG since I have no idea what the components in this system last used.

The FSM calls for 4.9oz of mineral oil +/- 1.2 oz, so I used 4.9oz of Ester Oil.

I plan to charge it with roughly 28-29lbs of R134a but we’ll see what the pressures like and how cold the air is that comes out.