88 Suburban - R12 to R134 questions

[tj43]

Hey everyone. I know lots has been discussed on this topic, but I was hoping to consolidate a few of my questions and get some experienced advice on my specific plan.

My 88 Suburban V10 has rear AC. It still runs on R12. I put a new Delco pancake compressor and OEM oriface in it last year, recharged with R12, and it worked for 6-8 months before the system discharged. Obviously, I have a small leak somewhere. I think it is time to convert to R134. Servicing and re-filling R12 is just getting too complicated. Less and less places have R12 or want to work on those systems. My plan is this: convert to R134 and then track down the leak (I am thinking it should be cheaper, easier, and more environmentally friendly with R134 than with R12).

Steps for the conversion: The compressor I bought and installed last year is R134 compatible, so I am good there. I see mixed info about o-rings, the dryer, and the oriface. What parts do I need to make sure everything is R134 ready? Finally, I am confused about the refrigerant/oil measurements when we inject the R134. How much of each do I need and what ratios (keep in mind, the Burb has rear AC so it takes a TON of R12). Also, when tracing the leak, I have seen some say that the UV dyes are not good for the older AC systems. Should we avoid the dye and use a refrigerant sniffer?

I want to do it right, and do it once. I dont want to go broke, but I dont mind spending a little extra to cover all my bases. Thanks for any help or advice you have to offer. I sincerely appreciate everybody's help.

 

[gmbellew]

if find the leak now before you convert. likely there was dye in the last charge, so get a UV light. replace accumulator and orifice tube. flush all the lines out with AC flush before you put the new parts on. you can reuse the compressor if it is good, but it would also be a good time to switch to a sanden. there is a good thread on this site about sanden conversion with the stock lines, so search it out

 

[Ricko1966]

If you want to find the leak now,I would. Get a fitting and hook your A/C to an air compressor, get busy with a bottle if soap and water,just like looking for a tire leak.

 

[bucket]

Proper way or not, you can get away with a simple "blow n go" with 134a and it will last for many many years, as long as all components are in good working order. I do highly recommend pulling the system into a vacuum first. Also reduce the charge amount to about 4lbs for a Burb with rear air.

The leak could be anywhere, but it is also HIGHLY likely that a rear AC line is leaking, where a mounting clamp is located.

 

[gmbellew]

Proper way or not, you can get away with a simple "blow n go" with 134a and it will last for many many years, as long as all components are in good working order. I do highly recommend pulling the system into a vacuum first. Also reduce the charge amount to about 4lbs for a Burb with rear air.

The leak could be anywhere, but it is also HIGHLY likely that a rear AC line is leaking, where a mounting clamp is located.

4.36 is the "chart" converted r134a great for a rear ac burb. I just did mine a couple weeks ago and it is cooling great. previously sanden converted.

agreed that the back lines can leak. the rear expansion valve can be tricky. i had to lose the brass spacer and use 2 orings to get my new one to seal. get a cheap uv light (a kids invisible ink pen has a uv light on it) and track down the leak and repair before you go down any conversion rabbit holes and waste time and refrigerant.

 

[tj43]

Closing the loop on this one:

I had a mechanic buddy search for the leak, vacuum out the system, and then do a "blow and go" to R134. Sniffer turned up nothing so we resorted to a little UV dye. The only leak we found was at the back of the compressor. We changed out the hose seals and it seems to have stopped the leak. Truck is blowing cool now--not freezing, but good enough to keep the truck comfy in the current Arkansas 110 heat index with 90% humidity. I am pleased. Fingers crossed it continues to work moving forward.

The engine hates the compressor, but I think that is normal for these R4s. It is much noisier and slower with the AC running.

 

[fast 99]

If this noise is from the compressor check for loose mounting bolts and that all the brackets are there. Depending on configuration there might be small bracket on the lower rear. If not there it will rattle like it has a rod knock.

 

[tj43]

Nothing like that. Just a higher, more labored idle and a bit more load on the engine at all RPMs. I am relatively certain it is normal.