IslanderOffRoad said:
I hate a/c threads becuase I never feel like I get anywhere with my answer.
I'm more confused than I would have been if I bought the damn thing and just tried it. I wish my a/c would just effing work.
Most of the answers seem to be in the thread.
The filler valves are different for an R-12 and R-134 system. When you say swap the compressor, is it with the valves? Do the existing hoses (plumbing) match the different valves? Does your replacement compressor fit the mount or does it come with a mount? Check the oil in your new compressor.
Guys have swapped over to 134 using the R-12 expansion valve, but changing to a R-134 expansion valve (if it wasn't already done in your last R-134 conversion) would probably work better, it was recommended to change the valve anyway because it may be plugged if your last compressor had a mechanical meltdown. You might try cleaning your old expansion valve if necessary and you want to try cheap. Expansion valves are freon specific, but most of their function is temperature control and the temperature difference between R-12 and R-134 is likely minimal. You may still have the R-12 expansion valve in your system (it usually says what type valve it is on the top), I don't know if it was replaced during your R-134 conversion.
The old oil left in the lines is likely contaminated, with trash, moisture or maybe what caused your original problem, which may have been incompatible oils. R-12 and R 134 use different refrigerant oils and from what I understand they aren't compatible.
Replacing the filter is always advisable, they remove moisture and moisture inside the system is real bad. The filters do eventually absorb all the moisture they are going to and become ineffective.
Pulling a vacuum on the system is recommended, the next best thing is a refrigerant purge, to remove as much air as possible. Air can really run the pressures up quick (over pressure), air contains moisture and air doesn't help any with cooling.
I'm curious as to what type of compressor you are getting. I don't know it to be a fact, but I've heard sometime in the late 90's they changed to a capillary system instead of an expansion valve (a good question for 5-90 to research).
Not many answers, but maybe a few usable questions. I've got no doubt I could make it work, i have a garage full of fittings and refrigeration tools.
If you decide that the newer compressor isn't going to be simple or easy to install and decide to go back to an R-12 compressor (which will pump an R-134 system with some additional stress) you may have a leak problem because of the higher pressures. Though it was mentioned that the highest pressure, isn't that much higher. It's recommended to change the HPRV (high pressure release valve) from the R-12 type to the R-134 type. And you are going to have to change the oil in the new compressor (if an R-12 type) to an R-134 compatible oil.
The high pressure relief valve makes a heck of a racket when it releases and sounds just like a bad piston or broken rod. Lowering the pressure a little often lets the valve reset and the noise goes away. Changing to a R-134 HPRV, may keep the system from popping the R-12 pressure release valve at typical R-134 operation pressures.
Some of what I've posted here is Sanden specific, but there are other model compressors in XJ's depending on the model run and sometimes there just different in the same model year.
I detest working on automotive systems, they aren't mechanic friendly.
Some of the guys on the board may have somethings to add or correct if I've misspoken, forgotten something relevant or made a mistake.
