Hello everyone,
I just wanted to post a follow up to my 1993 Jeep Cherokee XJ A/C repairs. (original post here: https://autoacforum.com/viewtopic.php?p=25581#p25581). I had some service valves leaking oil at the compressor, so I needed to open up the system. I recovered the refrigerant from the system (recovered almost everything I put in almost 6 years ago, so any leaks were extremely minor). I purchased new compressor valves, an updated parallel flow condenser from a 1997-2001 cherokee, custom made some hoses for adapting the new condenser, and what I believe to be the biggest factor to the success of this repair, an OEM expansion valve. The valve was a salvage part with some oil and gunk around it. Understanding the risks, I decided to clean the valve with an ultrasonic cleaner using distilled water and a cleaner called "Shellac buster" which is formulated for carburetor cleaning. It's gentle on gaskets and seals but has good carbon/gunk cutting power. I also performed a rinse with distilled water in the ultrasonic cleaner, followed by a thorough drying with nitrogen. The valve cleaned up well so I decided to use it.
Buttoning up the system with all the components, I performed an overnight nitrogen pressure check around 100 psi and it didn't drop. I performed a triple evacuation and charged with 2.15 lbs of R-12. I intentionally charged less than the factory 2.38 lbs due to the lesser volume of the parallel flow condenser as compared to the factory serpentine design. The sight glass was full and adding more refrigerant did not have significant impact on pressures, so I think I was pretty well in that sweet spot of just filling the receiver with liquid.
Over the last few months I have gotten outstanding results. Just the other day at 90 degrees and 63% humidity, I was pulling around 40 degree vent temps on medium high blower speed going down the road around 45 mph. Even at idle, it was still blowing around 45 degrees. This is on a system that previously could barely do that at 80 degrees ambient.
I hope you guys like the detailed posts as I appreciate the technical knowledge you guys pass along from various posts and I learn a lot from you guys. My biggest takeaway here is that whenever possible, try to find an OEM expansion valve or orifice tube and especially so if you are still running a stock evaporator like I am. I believe the aftermarket valves are tuned (at least for the Jeep XJ) for plate/fin evaporators, which I can say from experience do not perform well on an older tube/fin evaporator design. You could also say that given that today's aftermarket valves will be tuned for R-134a that would play a role in performance issues, but I think that's pretty minor. One final detail that I forgot to mention above is that I used some foam strips to seal around the perimeter of the condenser where it meets the radiator. This ensured that there was no "lazy air" bypassing the radiator and condenser. I think that's an often overlooked detail that helps draw maximum air thru the condenser and radiator.
Anyway, thanks again for all the advice from the experts on this forum and I'm happy to be able to post a success story!
-Matt