Is there a document available that details exactly how the A/C system functions on a 1994 XJS? I have a pretty good understanding of the components. What I’m interested in is how, from a user standpoint, the controls work and what to expect.

 

You have the Delanair Mark III HVAC system. I posted several references in several posts towards the end of a thread on the "other" website. Hope I don't get in trouble for this link.😆
https://forums.jag-lovers.com/c/xj-s/29

 

There is a separate document that came with the owners manual for climate control for that year.
It was sort of a folder if my memory serves.
I don't recall it answering all the idiosyncrasies of that system.
That one has lots of quirky things that clutter all the Jaguar forums.

 

I may have that manual. Ill post pics. The system sucks. But my issue is probably a compressor not pushing enough cold air when I really need it

 

Do you mean the blower?
The compressor is not pushing air, only freon.

 

Blower is fine. Its the freon thats not moving about like it should for consistent cooling

 

I have a new 4 Seasons A/C compressor w/clutch, expansion valve, and receiver drier all new in box for sell cheap if you would have an interest / need.

Parts are for the 4.0 engine.

 

We are having issues with the air conditioning system on our 1994 XJS. Compressor not engaging. Does anyone know where I can find or buy a full schematic of the electrical system? All help and advice is appreciated. Gerry

 

For a diagram, check at the top of this area, in the stickies. Lots of useful info has been loaded in there.

 

Thanks, will dig deeper when a little time available. What is amazing is that nothing beats the actual experience of members and their efforts. It seems seldom that someone has a new problem not faced and overcome by a member previously. With my mechanic wondering that the expansion valve may need replacing due to higher high side pressure, I'm wondering now, after reading some experienced comments, if possibly the supplemental cooling fan not working may be a first fix issue. The mechanic went through the system, evacuated, replaced drier, converted to R-134 and recharged. It immediately cooled pretty good, not as good as new with R-12 but I've always thought R-134 conversions didn't produce quite the differential of original...could be wrong on that. We drove the car about fifty miles, cooled great and then drove around very slowly on a hot day with AC on "cold". After about fifteen minutes it was blowing warm and the compressor not engaging. Also the supplemental electric fan is not engaging. With other vehicles, I've had the compressor disengage under hot standing conditions but always reengage when air flow over the radiator is restored. This time, when returning to highway speeds, the compressor never engaged again. If an evaporator high pressure issue then it would seem likely all would work well for a period if all is shut off or when pressures equalize for at least a short period.

 

where are you located?

 

Highland, IL.

 

where are you located?

 

Highland, IL. 35 miles straight east of St. Louis, MO.

 

Do you have a sight glass on the dryer?
If not, how are you determining freon flow?

 

My freon is not low. Compressor is simply not doing its job properly. I filled it last summer and from the get go, cold air is barely cold and then there are times when it seems to want to be. I do wonder if hot air is blending in. Will have to get it checked out properly by my mechanic. Im not great with AC stuff

 

You can check the high pressure switch by pulling the plug off of it and jumping the two contacts.

I'm not sure how to check the expansion valve. Replacing it seemed to resolve my cold AC issue...I think. I also replaced the two valves, at the high and low pressure taps. Highly recommend it. Not expensive and probably overdue.

Wiring diagrams? go to

jagrepair.com

 

How do you know it is not low? Is it overfilled? You really need a set of gauges to test it.

 

yes, its been tested.