When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a 72 Cutlass S, My A/C system was in op so i tried to charge it with R12 and it wouldn’t take the charge like there was a restriction. So i broke down the system and started blowing compressed air through it but didn't find a restriction. What i did find is an orfice tube near the dryer with a fixed orfice in it and no expansion valve or poa. I pulled and cleaned the orfice there was minimal debris. I also found that my compressor was leaking severely so i swapped the compressoR with the one from my abandoned supreme project. Since it had a fixed orfice i decided to charge it with r134 and it is exchanging about 42 degrees. My question is: have any of you seen one of these systems Modded to a fixed orfice system. I looked on rock auto and 1980 cutlass dryer matches what is on my car. My 72 supreme has the expansion/poa valve setup. Here is a pic of the dryer setup.
just wondered if you guys have seen this done before. I have only had the car since November. But i will say it seems to work pretty good.
If the drier fills with moisture, that'll be restriction enough. Thus, in need of replacement. I've never heard of just replacing R-12 with R-134 just like that, on an R-12 system
Got to make sure there's no mineral oil typically used in R12 systems in there with 134a. It doesn't mix well with 134 and won't carry through the system. And I hope you're pulling down the system with a vacuum pump to get rid of as much moisture as possible, or no matter what refrigerant you're using isn't going to work as efficiently.
It looks like your original AC system has been modified from it's stock configuration. I don't see a POA valve or an expansion valve in your picture and the big silver cylinder looks like an accumulator & cycling switch from a VIR system. Here's a pic of the evaporator suitcase from a '72 Cutlass. The POA is in the middle of the "S" shaped tubing exiting the top of the evaporator. The expansion valve is the small disc shaped part below it.
Thats what the system on my cutlass supreme looks like. Yes i did purge the system of mineral oil and added ester. I have a master cool 134 machine so yes i vacuumed it before charging and then charged it to 85% of capacity. I said it seemed like a restriction but it was the compressor that was the problem. I left out some details trying to keep the story from being too Long. I was mainly curious if anyone has seen this conversion before. It seems to work pretty good.
I haven't seen that type melded into the older system, but it's simply an newer system that works the same as the old stuff pretty much, just with newer parts. Although most people try to stick with the OEM style stuff. If it's working for you, great. One giant plus- You don't have to mess around with that "monkey sh*t" anymore trying to keep the TCV bulb stuck right up next to the Evaporator tube.
That conversion should work OK. From what I have read here, the only issue is the old style compressor is not designed to cycle on/off repeatedly so there may be more wear and premature failure.
On a '77 Vette had a VIR changed to accumulator and orifice tube, worked fine.
I don't see why it wouldn't work on a POA system. It's just a different way of controlling the refrigerant flow.
Maybe if you tweaked the compressor cutoff switch down a few pounds it may stay on longer. It's usually wise to do that with 134 conversions anyway. Every 1/4 turn on the screw counter clockwise will lower the cutoff pressure by about 4 psi. That may keep you from cycling too much. If you go clockwise, it'll raise it by about 4 psi. So for 134a, you'll need to go lower. Try the 1/4 turn CCW and see if that doesn't help your cycling times. You can see the little screwhead in-between the spade blades on the pressure switch when you pull off the connector on the accumulator.
Thanks for all of the suggestions, I will definitely look at the pressure switch to see if it is adjustable. I drove the car to work yesterday and the temperature was 102 on the way home and the system worked perfectly.
Just wanted give an update. I adjusted the pressure switch as recommended and the cycle times decreased quite a bit. I didn't time them but there is definitely a difference. The register temp is about 52 degrees at idle and about 42 at cruise speeds. Overall it is working really well. I will update in the future if I see any adverse a/c clutch wear.
Why would the clutch wear? What did they change in the clutch when they went to the CCOT system?
Far as I know, it's the same clutch, same compressor up until they started installing the R4 "hand grenade" compressor. With the early R4s, clutch life was longer than the internal connecting-rod/piston life.
I was just referencing some comments made earlier in this thread regarding clutch wear. I personally dont think its going to be an issue. The clutch looks just like the one on my 1999 pickup. And that clutch lasted 200k.
