My '93 aparently still had R12 in the A/c (bought from original owner 14 years ago, it still has original fittings, and finally lost pressure last year).
I'm going to convert to 134a, but I'm concerned I should drain out the old oil (which I'm sure is factory and probably... mineral oil?) before refilling with ester oil.

Is tehre any truick to doing this? I don't see a drain plug on the compressor... so does that mean the only option is to disconnect the lines coming in and out, unbolt it from the block, lay it down and flip it over and drain out through the connectors?

Option B of course is to just replace the receiver/dryer and fittings, purge, refill, and call it and day and see how long it all lasts.

Oh and yes I know I have a leak but to find it I have to have something in there running w/ dye. Its a really slow kind of thing, it hols vacuum for a long time etc

 

I saved the Toyota TSB on AC conversion another member posted a couple months ago. (PDF file below the image on draining oil.) The kit with fittings and orings are still available from Toyota

Below from '88 FSM on draining oil from compressor.

 

Great - so yes, have to remove and replace the compressor.
Man I'm just not feelin' it on this one.

Anybody have experience with not doing it and just swapping the receiver/dryer, drawing a c=vac, refilling w/ 134a and calling it a day?

This vehicle is rarely driven, we're talking like 1-1.5k a year with maybe 15-20 hrs total with the A/C running.

 

That’s exactly what I’m doing. R134 valves, replacing o-rings, flushing and adding correct oil to all parts, new drier and expansion valve and drier. Hoping this weekend to draw a vac and charge.

 

why replace the expansion valve?

 

Pulled everything out for o-rings and not knowing what all I had so made sense to swap it while I’m there. Evaporator and blower motor was full of stuff.

 

Is everything good now?

 

I’d roll the dice on option B. That’s what i did. All it took to make mine work was 1.5 cans of r12 and it’s been about 3 years.

 

turns out... no
but not catestrophic
I went with Option B - roll the dice, refill as is and go.
I vacummed it out (as I have before), it held pressure for a day, Added in my 134a.
The odd thing is - it took foreeeeeever to suck in the 134a. Like 45 mins for the first can. Then I couldn't get more than about 6 mor oz in (for 18ish total) which I know isn't enough. Vent temps got cool but not cold. However it was reading like 45 and 250 (can't remember) overall very high. So I shut it off and let it sit.
Low and behold, a week later - zero pressure at all.

So I must have a leake of some kind. I suspect it may be o-ring or seal related since it holds a vacuum just fine, its only udner pressure it leaks. And don't know WTF is up w/ the slow charge or weird maxes.
I'm wondering if the R12 to 134 adapter fitting on the low side may be questionable... I *think* there is a needle in there that actiates the original Scharder valve...? Wonder if it is sticking and is pulling closed on vacuum but not completely sealing on pressure, and also is not fully opening to let the incoming 134a is?
Oh, and I realized I may be letting a little air in because I used the same fitting end from my vacuum to connect the 134a can.... and guess its possible that line (up to teh site glass) refilled with air in teh exchange. Next time I'll open the can first then lossen the threads and purge it out a little before opening the manifold valve.
but I guess its time for some flourescent dye. Open to any other ideas.