Guys
I have a friend with a series III V12 XJ saloon 1989 model. There is no 12 volt feed to the compressor. I have downloaded the manual that Doug put up about 2 years ago, and that says pin 20 on the "grand piano" aircon ECU is what should trigger the feed to the compressor rely.
There is a fuse in line to the relay. I know how to change the fuse (once I have found it!) and also test the relay (ditto). BUT can anyone tell me how I test the pin 20 output on the aircon ECU? Somehow I have to test it when it is plugged into the loom plug, and I do not know how, or even how to find pin 20.
Any other help anyone can give me about the Delanair III system system as a whole would be greatly appreciated.
Greg

 

if the pin 20 output goes to the inline fuse, test the live side of the fuse holder to ground

BB

 

Thanks, If I can find the fuse!

 

If it's like mine you will find the fuse in and around a plastic black cover on the RH side back by the fire wall. Near the bonnet clamp mechanism. It's weird, just hanging around there, no discript...

I'll go to my (and relive some painful early days of looking at EDs of the xjs) and see if I can help BUT off the ed I got the color (I'm remembering black and green) off the piano and i took a reading there. The issue is that the wire from the piano makes a stop in the dial (I think) of the HVAC control before heading of to the relay to control/trigger it... Mine only gave 3.8v or something for some reason, not enough to fire the relay. For me, getting a new piano was out of the question, but maybe some day. I hot wired the relay and got a toggle switch to turn in the AC and everything worked from there. Even the little supplementary air valve kicks on...

Here's the diagram I remember hating, lol
Imma look and see if I can remember my chase. One sec

 

Sorry. It's the GREEN & BROWN which changes over to the PURPLE & BLUE before turning back to GREEN & BROWN after the rail temp switch... Drove me nutts, which ain't hard.

I basically lost "sight" of it when it entered the mode control switch and reemerged as purple and black. I also don't think I ever read 12v at the piano, either...

Now that I have a floor and seats in my car I will take the plunge with ya here,,, to see if a little calmer and a little further along in my progress will equate to patience, God willing

 

Thank you very much JJJ, that is really helpful. I am seeing the car on Monday, so i will post what we find, if anything.

 

Mannnn! My pleasure. This hasn't been a two way street. You be giving more than you be getting, at least with me!

EDIT - I think it's BLACK and PURPLE,,,, NOT blue and purple.

 

Any guidance on removing the unit from the car? I am at that point with my parts car.

Steering column is out, dash trim is removed, center console is out. Two vertical support arms connecting to the trans tunnel have been unbolted. Thx

 

Mannnn,,,, that's way outta my comfort zone. Never been there. I would say just keep digging,,, labeling nuts and bolts... Wish I could help ta see what's going on in there.

 

Brad
The unit is bolted up to the firewall in about four places, very easy to find the bolts. The hoses on the engine-bay side of the firewall must be disconnected from the expansion valve; then the entire unit should be pulled rearwards which it away from th dash and also pulls the expansion valve through a specially sized hole in the firewall.
This is best done with two, and be careful to note as you gently pull it rearwards a bit at a time, where all the tiny vac tubes go, as it is easy to pull them off their vac solenoid spigots and then impossible to know what went where.
From dim memory, I think the unit is bolted to the vertical bracers, but even when they are undone, it needs a good pull to get it unstuck from the firewall. There are the water pipes to be undone in the engine bay, as well as loom connections, the air temp tube, and the drain tubes to look out for as well.

 

Guys
Today's news on the Delainair mark III:
I went over to Monsieur di Benedetto's workshop ans there was an absolutely PRISTINE V12 XJ mark III Saloon in Solent Blue. No rust, it could have come out of the factory yesterday.
Armed with the manuals and diagrams Doug, JJJ and Grant and others kindly provided, we did some tests.

1. There was voltage to the compressor (testing with ignition on, mode switch to Defrost to over-ride the warm-up phase before which the system will not start). Thus no worries about the ECU, relay or fuse.
2. The earth from the compressor is a loom wire that disappears down the V to the firewall somewhere. This earth was not capable of transmitting a high enough voltage to engage the compressor clutch, barely managing 10 volts.
3. We ran an extra earth from the compressor to the rad panel and voila! all working.

Many many thanks again for all who helped. I explained to my friend that the finest Jaguar XJS and XJS Series III experts from three continents (London, Paris, New York, Seattle, Adelaide, Texas etc etc) had contributed over the weekend to my new-found knowledge of the Delanair III and he was suitably impressed.