i have 93 4.0 xjs. r 12 freon. ac was only working a bit. compressor engaged but very little cold. Something was left in the system. So i found a guy to add 2.3 lbs of real r12. we got the temp into the 50s with residual pressure reading in the system at 40 lbs. I assume there is a very small leak since 1993, but I hope it makes it for the summer. Here is the question:


how much Freon r 12 does a 4.0 93 take?


is 40 lbs pressure in the system too much? He was an AC guy and felt that it could go up to 50, but 40 was reasonable.


we were targeting a temp in the low 50s.


thanks


rich

 

Where did you find R12? 'round here it's impossible to find. Are you sure it's R12 and not a flameable drop in replacement?

2lbs as far as I know. Should be sticker somewhere in the engine compartment.

40lbs on the low side at idle seems a bit low. What was the ambient temp? could be right if it was cold out side. It's better to diag an AC system using high and low readings but some people shy away from the high side for safety's sake. You really need both high and low side readings and ambient temp to properly diagnose.
With r12 you could get it into the mid 30's

 

I am sure it was r 12. it was an old can with the doupont sticker on it. a back yard ac guy. nice guy.


based on your feedgack, I could have put a little more in. it was about 85 out.


nevertheless, it works well now and I am going to check all the connection points for leaks. maybe a little tightening and drive on. at 40 lbs I should not do any damage and will move r 134 after this runs out. hope to make through the summer...

 

Rich,


The best advice I can give you is to convert to R-134A as soon as you can.
Your car is now 20 years old and as part of the R-134A conversion have your "service pro" remove the hoses and replace all of the "O" rings, the
receiver/dryer and totally flush the system. My current experience (story below) has convinced me that half measures in AC service cause far more problems than they solve. Good luck!


My story;
I am currently rebuilding the AC system in my '90 Majestic. I bought the car in January and the PO told me at the time that the "AC compressor is a little noisy". OK, AC that needs work on a 25 year old car is really not a big deal. This week I was able to get into the AC in depth and what I found was a lot of screw ups and screw jobs caused by "AC pros" in the past.


The first problem was that I couldn't get the compressor clutch to energize. OK a review of the service DVD describes the superheat switch with its thermal fuse. I traced wiring, couldn't find the fuse, posted the question here and low and behold the service DVD is wrong! The '90 XJ40s (and others) don't have a thermal fuse!
Jumpered pressure switch contacts and a test light confirmed that so now...


Wednesday I really got into my AC and was astonished at what I found and what the pros did to my car and the PO (I have the original invoices for the AC work). I couldn't get a reading on my gage set and concluded that the system was empty. So... I very carefully loosened the low pressure line fitting at the receiver dryer and confirmed my initial conclusion. The the system was completely empty - nothing was in it; no refrigerant, no oil - nothing! I dis-assembled the entire AC system and it was so full of leak detection dye that the stuff came pouring out of the receiver/dryer, AC muffler and the high pressure hose to the muffler. The dye and no compressor oil had destroyed the compressor. I have to replace the compressor, receiver dryer, and the expansion valve (original is full of dye), flush the evaporator and condenser and pray that they are both OK. The gist of the story; the pros had chased a leak with an outrageous amount of leak detector dye, recharged the refrigerant, never found the leak, never evacuated the system and in their search for a "quick buck" destroyed the AC in their customer's car. I should have my AC completed and cooling my car by the middle of this week.