I'm still in the process of bringing this 81 XJ6 that's been in a garage for 17 years back to life. Yesterday was first long trip on a cold day. Heater worked fine, the wife and I were comfortable, I adjusted the temp slightly at time, and heard occasionally the small electric motor run.
On the way home later that day, not enough heat, luke warm, and moving the temp knob had no effect at all and I could hear no electric motor.

To me this heater system is complex. First, am I right that the motor is the one adjusting flaps to adjust temperature? It doesn't adjust direction and volume of air, only the temperature, right?

If I'm right, the culprit is that that motor doesn't run. But is it the motor, the switch/knob, a sensor somewhere, a fuse? Are there any obvious places to look, is this a common problem? I've checked all fuses I could find, left and right (LHD car). And the hoses in the engine room going to the heater gets quite hot, so I don't think it's the vakuum thingy in the engine room.

Any ideas?

 

Assuming you have the Delainair 2 system, there is a cam/mechanical servo block that activates the flaps using signals to to electric motor. This cam block motor in turn is activated by sensors reading the various heater and cabin temps, and these sensors feed into an ampifier which then sends command signals to the cam block motor which adjusts the flaps.
The amplifier is a known failure item, and it is possible it has gone. It is also possible is the rheostat on the cam block which activates the motors has given up; this means the cam block is getting the signal but is not responding to them.
Luckily in the USA is a firm called JagAire, run by a very helpful guy, who explain how to test these items, and who supply working ones and also show how to fit them. That should get the system working reliably again no bother.
https://www.jag-aire.com/

 

First, here's a little reading which might be helpful:

https://www.jaguarforums.com/forum/x...basics-178058/

Servo not operating

It is complex

The servo adjusts temperature, fan speed, and air flow direction. The various rotating am operate electric switch and vacuum valves



Hopefully you found four fuses for the climate control.

After fuses, amplifier failure is the most common fault by far. I don't know of any way to test the amplifier. However, the servo can be unplugged and tested with a 9v battery. The temp sensors, temp switch, and mode switch seldom fail.

Cheers
DD

 

Doug, good write up in the link you posted, I learnt something. I guess what I'm looking for is step by step analysis before replacing/buying anything :-)

Just to add to what I already wrote:
I checked all fuses on the two boxes behind the panels. And I found the fuses I think around the heater, on the LH it's hanging loose, on the RH it's screwed to the box thing. Fuses seem fine.

I haven't mentioned this before, but the other switch behaves like this:
Bottom: off
Low: low fan
Auto: Always low fan, in an earlier XJ6 S3 fan speed would vary
High: high fan
Top: Fan full speed, demist flaps open, hot (until the other day, now only lukewarm)

Also, there's no cooling, previous owner cut the fan belt to the A/C compressor.

So if it's not just a fuse, could it be something that's stuck on this car that hasn't moved in 17 years. The servo motor noises we heard on the way out, were brief, in an earlier XJ6 S6 motor ran for 5 seconds? Maybe it's stuck?

If not, how do I diagnose if amplifier (don't know what it is and where it sits :-)) or servo is faulty?

Thanks.

 

As Greg mentions, Gary Crosby https://www.jag-aire.com/ has very detailed instructions on his site how to test the system and determine which component has failed if any. Gary also has NEW amps for sale, and refurbed servos (cam block).

No, I don't get a percentage, I've dealt with this guy more than once and know that he *Knows His Stuff!*
(';')

 

Also worth checking that the hot water valve in the engine bay is not stuck closed.

 

Seek out and buy (good luck!) the Delanair Mk II training manual. Or the factory service manual. Both have good instructions and trouble-trees


Delanair Mark II AC manual - Jaguar Forums - Jaguar Enthusiasts Forum

At the end of the day, though, contacting Gary is your best bet



"Seem" fine won't quite do the trick

Verify. Or you may waste time and money.

Often the fuse contacts are simply corroded...a very easy fix.

Cheers
DD

 

It's open, and hoses going into cabin are plenty hot...

 

Go to Jose's site and look at the bottom of the Home Page for Manuals, then look for the Delnaire Factory Service Manual.

 

Have you a link please?

 

https://jagupgrades.webstarts.com/order

 

With excellent help from Gary, I managed to get it analyzed to a wire breaking apart. The ground to the amplifier was hanging on in a few threads. With that fixed, all ok.

So thanks to Gary if he's on this forum, and thanks to Doug for pointing me in that direction

 

Jose and Bill:

Thanks to Jose for constructing the marvelous web page. Extremely good read. Easy to navigate and chock full of Jaguar information.

Thanks to bill for the link. This one worked. I could not open prior ones on this forum.


The day is off to a great start.

Carl