I have a 1988 22r that I retrofitted from R-12 to R-134a. I looked up the original R-12 charge and it said 27 oz. So I understand you are supposed to use less R-134a, and I used approximately 20- 22 oz. On the highway now it gets down to about 52 degrees, with R-12 it used to get down to 40. But while idling the temperature will go up to about 70 eventually if left idling long enough. So im wondering if anyone has found the exact best amount of R-134a to use for a retrofit, because I hear if your just a few ounces off it wont cool right. Thanks

 

Its 75% of the R-12 volume. So it'll be about 20 oz. Sounds like you may have an airflow problem through the condensor at idle. Just curious, why did you retrofit your system? R-12 ransfers heat way better then R-134a.

 

Yea I cleaned the condensor and straightened the fins on it but didn't help much. I converted because I had a small leak I couldn't find and figured I could afford a $6 can every 3 months or so. I did find and fix the leak and fix it just recently, it was the low pressure hose. I guess its because my condensor is to small to work with the R-134a.

 

Did you use a set of charging gauges when you charged the system ?, if not then your just guessing.

 

No but I used a digital scale to put in 20- 22 oz. which is pretty close to where it should be.

 

the fsm has a trouble shooting guide for air conditioning . you can find a link on yt for it. i was looking at the 85 fsm.

 

Yea I downloaded the service manual for my truck a year or so ago. I think my higher temperatures are just because im using R-134 which my truck wasn't designed for. But its alot better than no A/C.

 

could the evaporator fins be partly blocked, interrupting sticking air flow ?
i had a 86 and we just put the 134 a adapters and added the freon. my cousin charged it for me so i don't know how much he used. the guy i sold it to said it was still working good after a couple years. i know it is not the proper way to do a conversion, but i didn't expect it to work in the first place. and i wasn't planning on selling it.

 

I don't think so because I washed it a while back with CLR. Then spent a hour or so aligning the fins with a small screwdriver. Im thinking it might be because I didn't vacuum down the system, I just held the high side shrader valve open while shooting R-134A through the low side , then closing valve and filling it up. This was to try to get air out.

 

if it starts working after it set for a while it could be freezing up.

 

That may get you close, but with out a set of gauges your still just guessing. For the a/c to get as cold as it can you need the proper amount of R134a and you need to run about 3 to 5 psi of back presure on the low side for proper operation.