I don't know whether I should claim "success" on the AC project, since the proof is really longevity of the repair - but I've got nice cold air now.

I learned several things worth mentioning.

Six quarts of flush is about right to get the system clean. I found my lines on the compressor/condensor side of the system relatively clean with just oil. The evaporator had remnants of "black death" that I was able to flush out nicely with the expansion valve removed. The flush gun was used to push flush solution in one side, and a short length of old garden hose pushed up over the other side running into a bucket to catch the output. Fill the evaporator with flush, let it sit for awhile, and blow it out with air. Repeat.

The receiver/dryer came from the WorldPac system and was the more expensive of the two offered. German manufactured and looked to be OEM quality. The second expansion valve also came from the WorldPac system and was "Made in China" and had an Egelhoff logo on the sticker. That's the one I used because it looked better than the other Chinese evaporator I ordered earlier from another source. They were both labeled "R134". The condensor came via WorldPac and I am satisfied with it. Not quite OEM but good enough - I saw a design improvement in the area where mine started leaking, and it was a perfect replacement fit.

It has been more than ten years since I worked with any R-12 system, and I had forgotten just how much colder R-12 is than R-134. The first can of refrigerant goes in quickly, and I froze a finger to the can. That wouldn't happen with R-134. Rather than pull off the skin, I turned the can so that the liquid inside wasn't against it and waited for it to thaw loose. That took awhile and although I didn't lose any skin I got a nice freeze burn that hurt for a week.

My plan was to monitor low-side pressure with the gauge while estimating the high side using the sight glass. This has worked for me in the past. If I had to do it over again I'd go ahead and hook up the high side gauge to have a more complete picture. At a system charge of 28 oz the low side was running 35 or so psi at 1500 rpm and about 40 psi at idle - aux fan running. I felt this was a low-side pressure I shouldn't exceed and left the system at that level of charge. The sight glass is still a fine foam.

The result is quite cold air, although we aren't in much of a heat wave at the moment.

I have wondered how the expansion valve might differ from the original R-12 equipment to the replacements marked "R-134". Would the new ones be less restrictive to pass more R-134? That might explain the low-side pressure I am seeing with less than what I expected would be a full system charge.

The "X" was located on this new compressor and is facing down, so that doesn't bode well for longevity if it represents something to do with oil to the bearings as others have suggested. Of course at the moment the compressor runs silently which is great.

It would be interesting to hear of others that have found a compressor source with the "X" facing up. You would think OEM would do this, but I wouldn't be sure of it....

I suppose if it lasts more than five years that's a success.

Ken300D

Another note since I have been using the repaired AC system now for several weeks:

The auxiliary fan cuts in properly with the automatic pressure switch which was labeled for R-134a. I was concerned that the aux fan would not often cut in since the R-134a systems are known to run at higher pressures than R-12. However, the aux fan seems to be fairly aggressive in cutting in when needed - so I am pleasantly surprised.

Ken300D