I'm probably going to have to send this to a specialist but just in the event there's a simple fix for this, here's the problem:

System set to 65 (full A/C): Cold air from the defrost vents, trickle of cold air from the outboard vents, modest amount of cold air from the center vent, modest amount of cold air from the footwell vents on the side of the center console.

System set to 85 (full heat): Hot air from the defrost vents, trickle of hot air from the outboard vents, trickle of hot air from the center vent, FULL-BORE COLD AIR from the footwell vents on the side of the center console AND from the two vents that serve the rear seat footwells.

System set anywhere in between (say, 75 degrees): Warm air from the defrost vents, trickle of warm air from the outboard vents, trickle of warm air from the center vent, mostly cold air from the footwell vents on the side of the center console and from the two vents that serve the rear seat footwells.

There seems to be multiple problems afoot here. First off, most of my airflow is going out the defrost vents and the footwell vents on the side of the center console. Turning the main control to "LOW", "HIGH" or "NORMAL" affects the speed of the fans, but not the location of the air. Putting it in "DEF" mode moves everything a little more toward the defroster but it's still leaking out of other vents.

Secondly, is the fact that the car is dumping very, very cold air out of the footwell vents when I need full heat. My only choice is to disconnect the A/C compressor manually, which at least keeps me from getting freon-chilled air in the cabin, but the air going to the footwell vents is not getting warmed, either.

It's almost like the air is passing through two different systems. That which goes to the defroster (and trickles out of the center and outboard vents) is being heated or cooled in proper fashion. That which is coming out of the footwells is not.

The real problem here is that my lack of mechanical prowess means I'm capable of squaring off a ball bearing, so if the fix requires me doing major surgery, I'm going to have to punt to an actual shop.

Jess

 

I would not wast my time taking the car to an AC shop, unless they knew the DA Mk3 system well, it will cost you an arm and a leg.

Firstly I would pull the side panels off the transmission tunnel and check all of the connectors, clean them and plug them back in. From experience there is a chance of a leaking heater core, and/or the O rings on the input pipes. This causes coolant contamination of the connectors.

I have uploaded a diagnostic procedure that may help and included a link to my blog where I repaired my HVAC unit.

Jaguar XJS Restoration : XJS Delanair Mk3 Repair

 

Thanks for linking this. I'm not an expert on reading schematics and using a multimeter, unfortunately, but any information is better than none at this point.

BTW, when I mentioned taking it to a shop earlier, I meant a service shop near me that specializes in restoring old British and Italian cars. I haven't talked to them yet but I plan to do it soon. There's also a shop about 5 hours from here that specializes in two things, converting auto transmission cars to manual (which I'd like to do to this car, eventually) and A/C diagnostics on older cars. If I can't figure this out for myself I'll punt it to one of those two shops and grit my teeth about the bill.

Jess

 

So I had some time today and took off the two transmission tunnel covers, which was pleasantly easy. First, the LH side...



First of all, I'd love to know what that little black rubber thing on the far left is. It has three wires running to it. Temp sensor, maybe?

Anyway, I unplugged both the round plug and the rectangular plug above it, the one with the two large wires. And I found ... ta da! ... what looks like evidence of a leaky heater core at some point. A couple of the prongs in the round connector were corrodoed, as was one of the two prongs in the rectangular plug. I didn't have the optimum tools to fix this problem but did the best I could with a set of files. The debris wasn't "fresh" and there was no wetness anywhere around, that I could tell. So I put everything back together and moved to the other side.

And then I found this...




That red stuff was some kind of melted plastic or rubber. I feared this harness had been on fire at some point until I started scraping off the debris and realized the wires under it were intact. Something either melted above this, up in the dash, and dripped onto it, or it's an unknown substance.

Anyway, I threw the white flag and this point, because I couldn't get either of these connectors to unplug and I didn't want to force it. I put the dash back together and called it a day.

I do have an update to the original post: My fan speeds are all operable, but I literally cannot hear any movement up in the dash when I turn the temp wheel. The temp does change, however, when I move from full cold to full hot, although the air isn't coming out of the vents it's supposed to.

I hear nothing that sounds like a vacuum wheel, no sound of servos, nothing at all. All my fuses are in good shape -- checked every single one in the passenger cabin, including the inline fuse in that second pic.

Unfortunately at this point, unless I'm just missing something obvious, my next step may be to find someone in the Mobile/Montgomery/Birmingham area(s) of Alabama or the Pensacola, Fla., area that knows how to fix this A/C system.

Jess

 

If you feel you do not have the confidence to tackle this, print out the diagnostic info and take it with you to the shop, this will at least give them a head start.

When you rotate the temperature knob you should hear a servo motor running behind the dash.

Based on your assessment of corrosion on connector pins I would replace all of the connectors in this area, any corrosion will cause issues.

 

I have fixed a couple of these systems with nothing more than a good cleaning of all connections and grounds, as Warren says. There are several connections on each side of the heater case, identifiable by tiny wires. A couple of them on the LH side are up quite high and hard to reach. The grounds are on the vertical dashboard braces on either side of the case.

Even if cleaning connections doesn't fix the problem it has to be done or any tests/diagnosis down the road may not be useful or accurate.

At this point I'm not so sure you need an a/c specialist. A good, patient, careful automotive electrician might be more in order. A guy who knows Jags would be best but any good tech with the right technical data/manuals (such as linked above) can probably fix the system.

Cheers
DD

 

Warren, Doug:

What you suggest is on my to-do list for Monday. The shop that does most of my work on this car would prefer not to work on this particular problem. So I'm going to have to do some hunting. I'm going to print/email the Delanair PDF for the shop.

I know I have some ground issues in this car. I have to input the radio code every time I get in the car if I want music. The computer in the dash sometimes resets the clock to 0:00 and loses all its fuel mileage information between trips. The four gauges in the middle of the dash are inaccurate (the oil pressure gauge is inoperable, completely) and the illumination is generally dim.

Jess

 

Doug is correct with the ground issues, DOH I should have mentioned this earlier.

I removed and cleaned every ground point I could find while I had my car apart. Make sure you clean ALL the paint off back to bare shiny metal, use sand paper. Then add a star washer between the lug and the body, once its good and tight use seam sealer over the top with a paint brush to seal it up, no more grounding issues. Seam sealer can be bought from any car parts/paint shop.

 

Jess, I won't be any help on your system, as mine has a MKII unit, but I am interested in the shop that does manual conversions. I live in Madison, AL, so it might not be very much further away for me. Can you give us the name of the shop?

 

According to the installer list on DrivenMan, these guys: Petris Enterprises | GM Driveline and Performance Specialists

They're in Scottsboro. I used to live there for 2 years but I don't remember them. But I moved away in early 2004 and they might not have been in business yet (as Corvette Clinic).

Jess

 

Just a quick update ... yeah, I'm going to need a specialist for this one.

I just acquired an 87 XJ6 sedan with a fully-operational HVAC system, and in that car, I can clearly hear all the servos operating and the things people here have been telling me to listen for over the years. This is the first time I've owned a Jag of this vintage with a fully operational system in all modes, so I never knew what I was missing, really.

Basically, only the bare minimums of the XJS's system are functioning. The fan operates in the proper speeds and the compressor makes nice, frigid air. Beyond that, nothing works. The slider under the radio doesn't really do anything. Can't get the cold air to stop flowing out the foot vents when set to full heat, etc.

This will need a trained electrical surgeon, for sure.

Jess

 

Just so you'll know.....

That car has the Delanair Mark II system with a big gear-drive servo. That's where most of the noise comes from. Your '89 XJS has a different system ...Delanair the Mark III ...without that servo. The Mark III hardly makes any sounds at all, even when working properly.



Again, just so you'll know....

That's really just a subtle 'trim' adjustment to vary the upper outlet temps versus the lower outlet temps. It only makes a slight difference....and you probably won't feel any difference at all until/unless the system and cabin temp are fully stabilized

Cheers
DD

 

Well, fantastic...lol. So much for my deductive skills.

Mostly if I could just get the d*mned hot/cold air blend problem fixed, I could live with everything else.

Jess