I've put together a short write-up on the Delanair MK II system which I hope some will find useful.





DELANAIR Mk II Climate Control

Series II and III Sedans
Early/mid year XJS

What follows is an abbreviated and somewhat random compilation of basic information that might be useful to those unfamiliar with the system.

System identification. The Mk II system was used on Series II and Series III XJ6/12 and early/mid XJS models. It was replaced by the Mk III system circa 1987 calendar year. The easiest way to distinguish between the two is the temperature control knob: the Mk III system has a “Pull For Manual Control” feature. The Mk II does not. The Mk III system was not used on any of the Series III 6 cylinder cars. The name “Delanair”, by the way, comes from “Delaney Gallay”, the company that manufactured the system.

Compressor. It is normal for the compressor to operate in all modes, even when heating is called for. The system is designed to refrigerate all incoming air first and then heat it as needed. This dehumidifies the air. The compressor itself is the common GM “A6 Axial Compressor”. The “Ranco Thermostat” cuts the compressor circuit if the evaporator ices up. Compressor protection was by a superheat switch and thermal fuse until circa late-1986 when the “HSLP” (high side, low pressure) circuit was used.

Amplifier. The amplifier is the brain of the system, located behind the console LH cheek panel. Roughly rectangular, about the size of a small pack of cigarettes, and has round multi-pin connector. The amplifier's job to process input from the control panel and temp sensors and 'amplify' the result to a 12v output to drive the servo. Some original amplifiers have be replaced with a round aftermarket type that looks like a shotgun shell. If replacement is needed it is common to leave the old amplifier in place as actual removal is tricky....so don't be surprised if you see two amplifiers.

Servo. Located behind the console RH cheek panel. The servo is the workhorse of the system that mechanically operates the vacuum valves, switches, flap linkages, etc. It makes a whirring noise when the dashboard controls are adjusted. When troubleshooting a fault turn the temp control knob and simply listen. Hearing the whir is a good sign. It means the system is fundamentally operational and is at least trying to comply with requests from the control panel. Lack of the whir sound means system is fundamentally inoperative. You can't go very far in diagnosing other problems unless you first hear the whir. The servo can be electrically divorced from the system for testing.

Fuses. This is the best place to start if you don't hear the servo whir and/or the blowers don't work. There are four fuses, two in the regular fuse panel and two semi-hidden inline fuses behind the console cheek panels. Behind the left cheek panel is a fuse on the amplifier ground wire. Behind the right cheek panel is a fuse clipped to the side of the heater case.

Amplifier failure. Historically, amplifier failure is much more common than servo failure, and most other failures....except perhaps heater valve failure. Failure modes vary from an outright inoperative system to erratic or non-logical operation. If it comes down to guesswork and/or no other definitive fault is identified, replacing the amplifier is a fair bet. Diagnosing other system faults is more difficult without a known-good amplifier.

Heater valve. The heater valve on the firewall is closed only when full cooling is called for. In all other circumstances it is open. Vacuum is applied to close the valve. Vacuum is removed to open the valve. Sometimes the valve is mechanically stuck and might be brought back to life by exercising the actuator arm. In other cases the actuator arm operates freely but the valve is broken internally.

Defrost mode. Defrost mode bypasses the 'automatic' aspect of the system and defaults to max fan speed and max heat. If you get max heat and blower speed then, at minimum, you know that A) the heater valve is open and B) the blower circuit is at least fundamentally operational.

Center dashboard vent. The center dashboard vent is designed to open only when max cooling is called for. When max heating is called for most of the output will come from the foot well vents in the cheek panels and a smaller amount from the left-right dash vents. In 'blend' or stabilized mode the output will be from both foot and left-right dash vents.

Face level adjustment. Later versions of the system have a hot-cold slide control under the radio. This is to adjust upper-vs-lower outlet temperatures. It is a very subtle trim adjustment. You won't feel a difference until/unless the system (and cabin temp) has fully stabilized.

Vacuum check valve. If the system misbehaves in accordance to throttle opening/closing and/or engine load, suspect a faulty check valve. It's the black/white plastic valve in the engine bay near the firewall.

Blowers. There are two blowers which themselves seldom fail. More common is a failure of the blower relay behind the console LH cheek panel. The highest blower speed is available under three conditions: when max cooling is called for, when 'defrost' is selected, or when the mode switch is set to 'high'.


Cheers
DD

 

Hi Doug, great write up thanks for sharing


Added to the "How to" section


Cheers
Jim

 

Many thanks. I am befuddled by this beast and havent even started to understand it let alone work on it. Now I have a starting point :-)

 

Well done Doug.

 

I add my thanks, Doug, for the well worded descriptions of the II and III systems.
I saved it to be added to my voluminous Jaguar Lore collection.


At the very least, I know that the version in my 83 XJ wuzza six is the II version.


And, after it's lumping, it remains all alike except that the compressor is the one that came with the 94 Cadillac package.


I Erred a bit in the install. I had the condensor cleaned. I installed a new drier. But, I passed the opportunity to flush the envaporator. Shoulda,. woulda. coulda!!


I'll not contaminate this very useful thread any further...


Carl

 

Doug,
I have a folder named Jaguar Documentation. This has been added to it.
Thank you for taking this time.
(';')

 

Carl, you've never contaminated a thread as far as I'm concerned. You always have something good to say....be it informational, advisory, conversational, or simply a nice stroll down memory lane.

Cheers
DD

 

except that the amplifier in the Series 3 is located behind the Radio, not behind the Knee Vent panel, that's where the large Relay is mounted.

The amplifier being behind the radio is the problem, very difficult to remove the old amplifier, so you just disconnect the round connector and connect a new one to the connector, then you have to get creative to mount the new one in a new location.

so many parts, so little room.

 

That explains why I never found an amplifier in any of the S3s I took apart in wrecking yards! I only found fan relays!

Thank you, Jose, this has confused me for some time.
(';')

 

I guess it comes down to the semantics of the word "behind". To see or remove the amplifier you'll have to first remove the knee vent panel (what I call 'cheek panel') so it's fair to say that the amplifier is both behind the cheek panel and behind the radio. Would you agree?


You're right, and I touched on that in the write-up

Cheers
DD

 

most likely they've already been snapped up by others who were there before you !

The amplifier is easily visible when your remove the LH cheek panel.

Cheers
DD

 

Elinor,

it is buried way deep behind the radio, mounted to a "spring tongue bracket", (I don't know what else to call it, but it looks similar to one of those small plastic Kleenex dispensers made for automotive use kept in the glovebox?).

removing the amplifier from the bracket is an entire day's job, so bring lunch, because the "tongue" of the bracket is facing towards the engine, so the amp has to come off the bracket sideways, a total pain. I have seen this same bracket in Series 3 XJ and in XJ-S, which is even worse.

the solution is to bring metal-cutting scissors and cut the dammed tongue off, assuming you can get the giant tin snips sideways in there, haha!

 

Doug,

when I remove the "cheek panel" in my 1984 XJ, I cannot see the amplifier, zero, nada, maybe in later cars they placed it closer to the driver's side where it is seen?

here's a picture of a 1986 XJ-S V12 Coupe amplifier which I pulled, took me half a day of dismantling the entire center console and side panels, same place as my 1984 XJ-6. I walked out with the center console too.

 

Here's some pics that might help.

First is a diagram showing the approximate location of the amplifier, identified as item #1. It's nestled in there but you can find it if the cheek panel is removed.

Next is the amplifier itself, the original style

Third is the ingenious 'Servo", which is quite a thing to behold. However, as installed in the car, is has a plastic shield covering up the mechanisms

Cheers
DD

 

I'll take some pics of my own car next week and post them up

Cheers
DD

 

Thanks, Doug and Jose:


1. I've saved pictures of that famous/infamous AC amplifier to my Jag lore stuff.


I hope mine remains friendly during it's possible long sleep. Or, oh me, mebbe not.


On the last 4.2 powered trip, AC was doing well on a hot day in a particularly hot part of our state. If I ever get around to charging the system, I hope it resumes cooling on command.


2. A breaker's yard sourced Amp may or may not work? Just another complication?


3. I've a useful tool that just might help in the removal of an AC Amp. It is a knife like handle that allows a portion of a hack saw blade to be attached. Envisage a knife sans steel blade and a serrated saw blade in lieu of.


Poke it into tight places and in ands out and cut the "infamous" tongue!!


I've used mine from time to time, but not in that scenario. Very helpful.


Carl

 

It's incorrect for me to say the amplifier is 'easily' visible.

It's barely visible if you know where to look and what you are looking for

Here's another pic. Here, behind the LH cheek panel, you'll see the amplifier's round wiring connector and the inline fuse on the ground wire. Just follow those to the amplifier!


Cheers
DD

 

here's something that looks like the "tongued bracket" onto which the amplifier is slid under.

this is not the actual bracket, it is something that looks like it, the Jaguar bracket is spring-
metal and with very sharp edges, you WILL be cut so bring bandaids too.

 

Oh, the stair-step thingy! I saw one in the first wreck I took apart, but after getting it out in my very hands (had to take the whole entire console out anyway), I didn't know what it was so I left it.

Doug is right; when I went back for it next day (having thought better of leaving Anything behind) it was gone.

Sorry for the misunderstanding.
(';')

 

yes, that thingy, encased in clear epoxy so it cannot be easily opened, but openable it is, I sure would like to know what it is that fails inside, certainly an electronic part that can be replaced. These things didn't come from outer space you know.