I have a couple of issues....

That I am trying to sort out. The first one is the AC.

The XJ had her 18th birthday this past June and nothing have been done to the AC,... or heating for that matter. Recently, it seem to work on a 'when she want to basis' with no rhyme or reason that will aid in trouble shooting. When it do work it cools nicely. I am toying with the idea of buying one of those aerosol can of R134 with the gage attached and try to refill it if that is what is needed. The local discount auto parts store offer several types and brands of R134 including a synthetic version. Who have had experience with these and what would you recommend?

Next is the rear drive shaft.

I am currently using an OEM front drive shaft having remove the Tom Woods shaft because of vibration. In my mind, this drive shaft is on the short side. With the XJ at ride height, it have 2 inches of the slip yoke showing and what I think is only 0.5" of extended travel left. What is the basis for determining what the length a rear drive shaft should be? This drive shaft have a total of 2.5" of travel. My gut feeling will be to have one made that is 1.5" longer than the one in place right now. Would that be good or would it cause problems?

If it works good sometimes, I wouldn't try to add refrigerant. I'd try electrical checks such as the pressure switch or clutch with a voltmeter. Does the clutch engage even when it is not working?

winterbeater said:

If it works good sometimes, I wouldn't try to add refrigerant. I'd try electrical checks such as the pressure switch or clutch with a voltmeter. Does the clutch engage even when it is not working?

Click to expand...

Yes, I agree that it is likely to be an electrical issue. If I remove the relay and jumper the two large relay contacts (in the PDM) the compressor always engages and remain engaged until the jumper is removed. I have not gotten around to running more in-depth testing. What I do know is, with the AC on, the fuel mileage even on the highway at about 65MPH drops considerably.

Where is the low pressure switch (LPS) located? In addition to the LPS, could it be a ground issue between the PCM and the PDC (relay box)? The PCM does supply the ground does it, or is it the positive that causes the relay to close.

There is only one wire coming from the relay to the compressor which is positive then it divides near the compressor with one wire going to ground and the other going to the clutch. Why it this so? Is there some little do-hooky (a diode or something similar) where the wire divides that allow one wire to be negative and the other remain positive?

I had some time today to poke around in the XJ to get a better feel for the AC problem. Reading through some stuff leave me with some questions that I need help to answer.

1) How do one test the low pressure switch? The manual for the '96 indicates
it serves both as the high pressure and the low pressure.

2) What does the AC Cycling switch look like and where is it located?

3) The expansion valve. If this fails, what are the symptoms?

There seem to have plenty of pressure in the system when the valve is depressed even though the system have not been used for several days. I do not have pressure gages to test the system. I want to look at every thing I can before going out and buying equipment or taking the XJ to a professional repair shop. It is thing called saving money by doing as much of the work myself.