My 1992 4.0 Coupe, like many others it seems, has a problem with the air conditioning / heater. However from what I can see my issue is different to the most common threads as the entire thing is completely dead. It's a Delanair MkIII system which I know for sure as I've uncovered the 'grand piano' shaped ECU on the right of the heater unit and because it has the 'pull for manual' option on the temperature control.

Problem is the whole system is completely dead, no matter what you do with the two controls, nothing happens, the fans do not blow and no air comes through. When you drive the car for a reasonable period and the engine gets up to temperature then the cabin gets filled with hot air, but it seems that mainly comes from the demister and side face vents. No matter what you do with the 'face vent' control no air comes from the centre vents either hot or cold.

I've checked the basics in terms of fuses, but I'm struggling to find any relays that relate to the heater unit.

I've tried to make sense of the wiring diagram and measure some of the key pins on the ECU. With the ignition on I get battery voltage on SAC2-1 of the ECU, which seems to be the power in for the whole thing. I also get around 8v on SAC4-2 which seems to go to the Right Blower circuit.

It seems that the ECU is in a really awkward place, so I'm hoping that it doesn't need the whole dash to come out in order to remove it (any tips would be welcomed). I've read a few accounts that say you need to clean the pins on the connectors to the ECU, which I'm happy to try but wonder if it's possible to do in situ? I also read that the connector on the rear of the temperature selector can be a problem too but I'm not sure how I access that. I should say that I'm in the middle of a full leather restoration on the car, so currently have the seats and centre console (whole thing not just the ski slope) out of the vehicle which makes access a little easier.

Any pointers would be very welcome.

Thanks

Ralf

 

Having stripped the dash down, I cleaned the connectors for both control knobs and attempted to check some of the pins on the ECU. But other than confirming that there was 12v on PIN1 I didn't have much other success. After speaking to my local independent Jag specialist, I discovered that it's common for both fan motors to fail at once and if they are working then it's probably the ECU at fault. I decided to spend a little money and seeing as I'd already stripped everything down, then an hour of their labour could be focussed on diagnosing the fault rather than taking the dash apart. They tested the fan motors and relays and confirmed that it's the ECU at fault. So I've ordered a replacement from an XJ40 for £65 which looks visually the same and am hoping when I fit it next week that it will breathe life back into the heater/air conditioning.

I'll post a further update when I know the outcome.

 

Ok, progress update. I received the 'new' ECU yesterday and fitted it last night. Hey presto, my fans leapt into life and, after blowing out a load of crap having not run for a long while, they seemed to work perfectly.

I then spent the next 2 hrs cursing and swearing as I re-assembled the dash, refitted my newly reconditioned centre console and finally refitted the stereo.

 

Did you follow a writeup on installing a new stereo unit? Mine is dieing so I'll have to go down that path soon.

 

TBH no I didn't. Getting the old one out is easy as you remove the two heat controls, undo the nuts behind the plastic knobs and then the panel comes free. There are 4 screws holding the original stereo in place and that's it.

I debated what to do about mine in terms of spoiling the original look, but concluded that the need to not get fined for using my phone when driving meant I had to go for a modern unit. Brought a driverless head unit (i.e. no CD deck) that lets you stream from your phone and has an FM (didn't want to bother routing DAB antenna) and includes a mic for hands free calling.

I brought an adaptor cable on-line which was for the vehicle, but when I tried it, only the front channels works. After comparing the pinouts on the original connector with the ones from the stereo connector, I discovered two pins were the wrong way round, so I managed to extract them from the plug and switch them over.

The hardest part is finding room for all the cables behind the new unit. It's very crowded back there. It was easy to route the mic cable under the dash around the steering column and up the A pillar where the mic clips neatly at the top and works well.

What I've not solved satisfactorily is that the metal cage the new stereo clips into, doesn't anchor properly in the opening and the stereo pops out from time to time due to the pressure of the cable behind and lack of secure fitting. I'm planning to copy the fitting from the original stereo and 3D print a plate of some kind that will enable me to fix it to the original screw fittings that held the old unit in place.

I should also note that I ended up replacing both door speakers as I discovered that the cones had completely broken free from the speaker chassis due to a combination of rot and old age. That was an easy job, although I needed to drill new fixing holes in the doors because the old speakers didn't quite line up with the new ones.

Hope that helps

 

Good to know there is an adapter somewhere out there, I've found my speaker popping issue is somewhere inside the stereo itself, taking it out and giving the unit a smack helps for a day or two until you hit a pot hole.

 

If memory serves this is the one I brought Jaguar XJS 1987 - 1996 Car Radio Wiring Harness, ISO Lead - Car Hifi Radio Adapter.eu

 

I am having the same problem with my blower fans completely dead. 1989 XJS 12. Can anybody tell me how to check switch or module. Are there any hidden fuses?

 

New to Jaguar and this forum but wondering if anyone can tell me if the 1989 XJS 12 would be the same problem?

 

I did quite a bit of research. The first thing is to determine which model of heater system you have. Mine is the Mk3 which you can tell because the temperature control (left hand knob) has a PULL FOR MANUAL option. If yours has that then it's the Delanair Mk3 system same as mine so I can tell you what I did.

1. There are fuses in each of the left and right fuse boxes.
2. If you remove the ski ramp and centre console you can remove each of the control units and clean the contacts. Apparently the temp control is often corroded. Mine was a little but this wasn't the problem, unfortunately. I cleaned it with contact cleaner anyway.
3. The ECU is on the right of the centre console, above the fan control. It looks a bit like a grand piano and has three white connectors along the front of it.

I've spoken to a Jag specialist who services my other Jag and he told me that it is possible that both fan motors will fail together, but it's normally the ECU when it's completely dead.

Hope that helps

 

Thanks for the reply. I'll keep taking apart. Don't know what system it has but you turn the temperature switch to go from manual to auto. Tomorrows task is to remove radio and glove compartment trying to access blower control and ECU

 

This thread might help you more

https://www.jaguarforums.com/forum/x...basics-178059/

 

Thanks Again. I will Find the problem. Where do you find the replacement parts?

 

I brought one on eBay from somebody breaking an XJ40 (it's the same unit as the one in the XJS provided you have the MK3 heater). Cost me £65 and was fiddly but easy to install.

 

Because my Jag is a 1989, It must have a MK3 system (I think). Does the location of the parts change if it is a left hand drive . Mine is. Can't seem to find the ECU or amplifier on parts sites but I am not really sure what they look like.

 

Do you know if the Climate control ECU (piano shape) from any othe models will fit work on my 1989 Jaguar XJS convertible?.

 

I used one that came out of a 1989 XJ40. There are different variants apparently, mine had a spade connector in the middle of the five voltage regulators that stick out the back, I don't think all of them have that. Although the part number was different on the one I replaced mine with, I figured for £65 I'd take a gamble and if it didn't work I'd sell it on eBay again.

I hope that helps.