Hi All,
My first post here…
I have a 1993 XJS 4.0 convertible. VIN is SAJNW4743PC187443.
The A/C / Heater system is not working at all.
When I turn on the fan, even to ‘Low’ it only blows at high speed, even after running for several minutes. There is no cold or hot air, just ambient.
When I move the temperature control knob in or out I do not hear any kind of click engaging a compressor.
How do I find out what type of system I have?
Does anyone have a diagnostic manual / wiring diagram for whatever system I have?
Can anyone help me with a photo / sketch / diagram to locate the A/C system components in the engine bay and passenger compartment.
Any suggestions appreciated.
Bernard,
A/C is not something for the real men, so don’t worry and celebrate 
Prior to study of Kirbert’s link above - ask yourself when was the last time you saw A/C working? Was it last month, year or never?
Longer unserviced, bigger the chance that repair cost will be greater than the value of your Jag…
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@Kirbert,
Thank you for the link. Seems to give a good starting point and foundation for my diagnostic efforts. I’m not afraid to pull out my soldering iron and getting stuck in.
Is it a safe assumption then that my '93 has the Delanair MK3 (did they all have it?)
LOL ref the need for A/C and I entirely agree… I have only driven a handful of miles with the roof up, and those times purely for the comfort of my passenger.
I’ve owned the XJS for about 15 months now and bought it from a former co-worker who had owned it for several years before that. He tells me that the A/C worked for him but it never got very cold. He said that when it did work, there were probably 5 minutes of fan blowing before there was some kind of thump from within the blower system, then suddenly the air would start to blow cold. He also told me that he and his wife would use a piece of card to cover the middle portion of the center-dash A/C vent outlet to increase the amount of cold air they were able to direct to themselves through the ‘directable’ sides of that center outlet.
I need the A/C to enable me to enjoy more opportunities to drive it. I am lucky enough to have it purely as a fun car, but I would enjoy the opportunity to use it for my commute occasionally. I need to make calls during my commute and roof down on the Southern-California freeways is not practical for volume reasons, and roof up with no A/C is not practical for thermal reasons. I don’t have the money (or the inclination) to just have a garage solve the problem for me - a lot of the the fun for me is figuring it out and ‘getting my hands dirty’. I’m sure most of us can relate to that!
While I understand the principle of A/C systems I’m not sure where the main components are physically located in the car. That would be a starting point for me as I chip-away at diagnosing the issues and getting it functional again.
I am still hoping to find a seasoned XJS specialist / mechanic in the eastern San Gabriel Valley / Western Inland Empire area for pointers / brain picking / moral support, and look forward to leaning on the available expertise of this ‘Jag-Lovers’ community too.
The thump is one of the damper doors in the dash unit sticking, then suddenly opening. My 87 does it also. Sometimes pounding on the dash makes it open sooner.
The Jag AC is one of the easier ones I’ve worked on. All of the engine compartment components are on top, staring you in the face, at least on the V12. The evaporator in the dash is really only the hard thing to replace, as the dash has to come out. If yours hasn’t already been converted from R12 to R134a, I’d suggest doing so. There is a service bulletin on doing it.
Leak areas are common to most cars: compressor seals, bad Schrader valves, hoses, etc. Yours may just need a charge.
Read the section in Kirby’s book on the HVAC system, and most questions will be answered.
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@jal5678,
Thanks for the feedback and I’m glad to hear you find it easy to work on - gives me a bit more confidence I can at least manage some of the work on my own. I’ve never really done any work on an A/C system so learning as I go…
I have the 4.0 In-line 6 and haven’t yet been able to really take the time to figure out where the pumps, pipes, valves, vacuum lines, etc all run to and from.
Thanks for the reference to Kirby’s book - what a wealth of information!
Apologies if its a silly question, but how would I be able to tell if mine is R12 or R134a?
Usually there is a sticker in the engine bay stating the system refrigerant type and capacity. If the car has been converted from R12 to R134a (I don’t know if any of the 6-bangers in the US were ever R12), there will be a sticker too if done by a shop
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You usually can tell by the charging ports; R134a use a quick connect, and R12 are screw on. Note that the R134a caps screw on the inside diameter of the port and there are no threads on the outside.
Yes, I think all XJ-S’s had the Delanair MkIII until the end of production. However, there’s also the question of what compressor you have (earlier V12 had the Harrison A-6, later V12 and I think all 6’s had a Sanden), which freon (R-12 vs R-134a), couple of other things that changed along the way.
@sbobev and @RGK20m3…
Thank you for the feedback… from your comments it seems I have R12. See pictures.
- I’m guessing “Freon 12” is the same as R12.
Seems to be confirmed by the connectors I have…
As for the compressor… this is a quick look - not sure if there is enough detail here to help someone identify which one it is.
As I followed the hoses and lines I noticed some kind of sticky ‘goop’ around where the lines lead through the bulkhead. Is this normal?
Nope. Those connectors are adapters for R-134a. It’s been converted. It might have been done badly, explaining the poor performance. Properly done, a system with R-134a can frost up the rear windshield.
The sticky goop is meant to insulate the temperature sensor for your expansion valve, shown in the photo. This valve determines how much refrigerant flows through the A/C system.
It’s been converted to R134a because of those connectors. Get caps for them. Any auto parts store carries them. Very common for Schrader valves to leak, and the caps significantly slow down any leaks from the fittings.
Actually, I didn’t trust the sorry plastic caps to prevent leaks – and I had a known issue with the Schrader valves leaking. So instead of plastic caps, I found a stubby screw of the correct thread that would screw into those adapters. I then installed those screws with an O-ring that fit snugly around the screw and a flat washer that fit around the OD of the O-ring. Just snug it up, never leak.
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Good caps have o-rings also.
Yeah, but they’re still flimsy plastic junk. At least, all the ones I’ve seen were.
I reckon this is by design : flimsy plastic should be enough to compress the O-ring and prevent leaks, and will break before doing any damage to the thread of the port
anything stronger would be a risk of overtorquing by a garage monkey braking the port
if the sticky goop has been removed / badly refited, what is the best repacement ?
and what are the consequences if missing ?
If you have a plumbing supply store , or electrical for that matter, they should carry a sealing mastic that should work. Sometimes called “duct seal”, it’s purpose is to insulate the sensing bulb on the expansion valve. If it is missing, the expansion valve won’t allow the correct flow of refrigerant into the evaporator. You need to keep engine heat away from the bulb. You can also buy something suitable on line.
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