1992 Jaguar XJS Problem with stuck climate control vent flaps

I had a similar issue. There was no suction on the green line. I had to get to the pair of motors and reseat the electrical connector to the one motor. Knowing what I know now...I only had to pull the radio to get to the four connectors and reseat them. The connectors are on the right of the radio hole.

Is where I left it for now. Doug, your last thread helped me determine that the center vent vacuum servo actually seemed to be working (although I found it odd that it only seemed to open when it was set to the coldest temperature and of course only when the upper flap/ vacuum servo was in the closed position. I ended up disconnecting the upper flap and leaving it in the closed position so that I could make use of the cold air blowing out of the center vent. Finally, I ended up needing a new ac compressor and a new hose going to the condensor and now I have fairly cool air. I wasn't able to get more than 85psi R134a on the high and low side with the compressor turned off. Those went to 25psi and about 220psi at peak operation on a relatively cool day (65 to 70F).

Thanks for everybody's help. I couldn't have done it without your prompt and friendly advice.

Best Regards, Tom Colitt

Thanks a lot Doug.

That definitely sound like it's worth playing around with a bit more....

Tom, below is a cut-n-paste of a couple postings from a 2006 Jag-lovers thread. It is my response to a fellow named Ron.

Not sure if it's exactly on point or very helpful...but perhaps something will "click" and help you along

My thanks to Ron for heading me in the right direction. I never realized the
"inhibit" aspect of the other flap.

The system is now working properly although I am not sure why....which
leaves me with an uneasy feeling.

Following Ron's lead I went to the other vacuum motor. This has a green
supply tube and is identified as a demist flap actuator held closed by
vacuum. I applied vacuum and, voil?í, the center dash flap was quite easily
moved with my fingers. OK ! Now we're getting somewhere. Realizing I had a
control problem, contrary to my initial assesment, I reassembled a few
things so as to begin diagnosis again from a different approach

When enough was put back together to test the system I discovered that all
modes and functions ...including the denter dash vent....were fully
operational although I hadn't (knowingly) repaired anything.

I can only assume (dangerous, I know) that somehow the "inhibit" mechanism
had gotten out-of-phase and operating the demister flap *with the center
flap disconnected* had somehow allowed things to fall back to a neutral
position. If I am corect here I must say I have no idea how it could have
happened.

If I have trouble in the future I now at least have a understanding of the
system and will have a better starting point from which to diagnose the
problem.

My thanks to all who replied and especially to Ron who provided an
epiphany-esque clue.

Doug Dwyer
Longview, Washington USA
1987 XJ6 Ser III
1988 XJS V12 Coupe

From: "Ron Kelnhofer"

I just happen to have my complete A/C- Heater assembly on my workbench
because I'm renewing the evaporator and heater core. Although mine is a Mark
II from 1980, it may be similar in this regard to the Mark III. My upper
assembly has two vacuum valves attached, side by side approximately 3-1/2''
apart. The one farthest right is also about 1 inch higher than the other.

One on the left is directly attached to the center vent flap. The one to the
right is attached to a much smaller flap that is designed to inhibit opening
of the center vent. When vacuum is applied to the inhibit valve, the center
vent is now allowed to open.

Excellent. Thank you Steve. Yes, it's that hose with the canister in between. Seemed to be leaking after my dye test and now, no longer, but probably safe to replace it anyway.

Doug. If it's not too much trouble I wouldn't mind reading your old posts regarding the out of sync vents, but no harm if they're lost....

Thanks, Tom

I do! I think the hose/pipe you want is the one from the compressor to the condenser. It looks like it's two pieces, a muffler and a hose, but they won't come apart usually with out destroying one or the other. It's always sold as one part, P/N CCC2769.

Good luck!

Steven. Do you happen to have a picture that shows the area slightly to the right from that which is shown in your picture above? I am on the road, but would like to order a suspect ac hose so that I have it waiting at home for me when I get back. It runs on the right front side of the engine bay. It is a rubber crimped onto a steel pipe affair, but I'm not entirely sure if it originates from the compressor nor where it ends up. I'll know it when I see it in a picture though.

Doug. I've decided that I will have to just jamb the center Ac vent in the open position due to the involved nature of the climate control problem. I'm not even sure that will be easy, as manually tugging at the lever for that vent with the vacuum servo disconnected didn't seem to budge it much...
Thanks, Tom

Sorry, been sidelined with family matters for a while.

I'm inclined to agree Tom, you are probably at a point you need someone with some experience with the Delanair Climate Controls and proper service documentation. Sure sounds like a general failure to me as well.
Yes, your mode motors probably are without the brown pads on the sides as in the picture. That started around 1994 and was applied to service parts for the earlier cars; so it's possible to see that on one like yours, but only if there had been a replacement. The connector also was changed I believe in 1995, so the pictures are just representative.
And yes, the one vacuum actuator, with the green vacuum hose, does control BOTH sides of the demist vents, and the one with the black hose controls the center vent flap.
One thing to consider, or be aware of: the two blower motors force air to the center, and through the heater and evaporator matrices. If one motor is not functioning, the one that works just blows across into the other one, and it's very hard to tell if the vents and flaps are working or not.

Try to find a dealer guy or independent that knows something about the Delanair units.

Cheers,

I'll digest and mull what you've written. Maybe I'll have an epiphany :-)

Not sure if it'll help, as there isn't too much diagnostic info, buts here's a wiring diagram. Scroll down to Figure 23

http://www.captainjaguarscathouse.com/Electrical_Guides/XJS%201992%20Ele...

Cheers
DD

Edited on 2013-04-05 19:46:45

Wow Doug. That's interesting. Well, we already knew that the 12 cylinder wasn't built for fuel efficiency and apparently the AC system was built to contribute to that...

So, I spent some time under and around the dash and vents today. When I disconnect the right defroster windscreen vent linkage, nothing seems to change at all with the air flow coming out of the top. It's also hard to believe that the linkage on the right hand side controls all the defroster jets all the way over to the left hand side? (maybe so...). I disconnected both the green and black vacuum lines and applied a vacuum. The defroster linkage moves, but there is no change in flow at the defroster nozzle. The linkage for the center vent grill doesn't seem to want to move at all and seems jammed internally. Maybe this is the out of sync situation were talking about, but i don't see any way of undoing that without taking out the whole middle console an having access to that section. . When I turn on the ignition and the fan switch on, the check valves both click, so there seems to be general vacuum in the lines, although I can't say that I feel it when I put my finder on the end of the hose.

I also tapped on the mode motors (p.s. they are now black plastic housings), but I can't detect any changes. I checked the little orange three pin connectors (only two occupied) that look like they come from those motors (not the black connectors as shown in Steve's picture) , but it seems like they aren't working, since nothing changes and I can't feel the motors doing anything. (I'm not even sure what lever or temperature knob or fan setting is supposed to make them do anything. Maybe they all work together and are controlled by a processor?)...

Overall, I'm starting to suspect some general control unit failure since very little seems to be doing what it's supposed to and the only obvious thing that isn't as it should be is that center vent that seems to be jammed. I checked all Ac and climate related fuses and can hear some clinking of relays in the engine bay. I'm not so hopeful anymore of making progress unless you guys think I should continue and think I missed something or have any more ideas?

Thanks, Tom

Have you checked the previously mentioned motors as well? Are they rotating the shafts that they're attached to? Any response at all?

Normal for the a/c compressor to engage whenever the system in turned on, regardless of tmp setting. All incoming air is chilled (and dehumidified) first then heated as needed. So that's one thing you won't have to worry about sorting out :-)

Cheers
DD

I took out the glove box and found the two vacuum controlled servos. Even when I loosened the set screws on the linkages, I couldn't really tell that any of them were doing anything, no matter how I set the various climate control levers. All the 4 vacuum fittings at the manifold seem to be making a good connection. My Ac cmpressor is running at all times when the fan is switch on, whether I have the heat set to cold neutral or hot. I guess I'll have to dig deeper.

Actually, the out-of-synch problem I mentioned occured on my '88 XJS with the Delanair MkIII

Cheers
DD

Thanks, Tom, but the only "credit" I'll accept is for acknowledging my own failings. Like Doug, I'm foggy on the details way more than I used to be as a pup. As time marched on and I saw these cars less and less each day, I hit on pictures as a way to help jog my recollection of where thing ought to be, how they are mounted, etc. Back in the day when these cars were new, I could tell you where every part went, what tool you would need to remove it and the exact order of reassembly. It just t'ain't so any more; so I have to compensate.

The fog cleared just enough to recollect that what Doug is referring to is the flaps clashing on Delanair II systems. That was used on the Series II & III XJ6 and the XJS up to 1986. From 1987 on the climate system was the Delanair III unit. It uses the Mode Motors pictured above.

Happy hunting!

Oh, I guess I need to correct my signature as I am down to the XJR in my Jaguar stable. The XK8 now belongs to one of my Club comrades.

OK. Thanks Doug. From the picture it looks like those are on the right hand side of the car. I imagine the there are also some on the left hand side vents. I can't even imagine how I'll be able to work my hands all the way up there from the drop down fuse panel covers and I won't be able to actually take a look until later today. I don't recall there being many "holes" at all when I was searching for that elusive OBDII connector.......

Tom, if none of the above pans out, examine the uppermost vacuum actuators and flaps...the two gold vacuum cannisters at the very top of the dashboard pic above.

My memory is foggy on the details but years ago I had a vent control problem on my XJS where (as I recall) the flaps somehow got "out of phase" and were fighting against each other. I recall disconnecting one or the other, operating the system thru the various modes, then reconnecting.

IF you think it merits more consideration in your case I'll try to find my old postings on the subject which might have more details.

Cheers
DD

Thank you! Man, I can't believe how quick, helpful and knowledgeable you guys are. I try to do the same on these boards, but my field of expertise is the older Mercedes, specifically the Pagoda. Steve. I'm impressed with your collection of pictures. I see you don't own an XJS. Do you just have a collection of archive photos? And then you still have to import them into Photoshop to add the markings... Thanks again...

Vacuum supply connects at the rear of the intake manifold,
[oval] and heater water valve is at the center of the firewall. [circle]

Cheers,

Edited on 2013-03-26 13:17:38

That sounds like a quite likely scenario William. I think you're saying somewhere in the engine intake manifold. Do you happen to know the general area, since everything's so convoluted and difficult to see in there. (It was quite a chore to even replace all the spark plugs, cap and wires)....

I would suggest checking the vacuum lines in from the manifold and out to the heater valve. If OK find someone, -perhaps the club tool store- who has the AC systen tester, that way you can isolate the problem. The tester also allows you to move the system and position the system to hot or cold and leave it there,

Thanks a lot Steve and Doug, for the concise tips. I guess it's worth doing those few things before I try to jam the vents permanently. This is an otherwise quite nice SoCal car, although, not exactly well-maintained, so it's hard to see why there would be any corrosion on connectors and grounds unless they are very bad on Jags.... Everything else still seems to be working. Maybe some vacuum leaks are the cause, but I really don't see how I'll be able to get to these servos from under the dash....

While you're rooting around in there clean all the connectors. Look for the tiny wires with corresponding tiny connectors. There are several of them, including at least one rather high on the left side...hard to reach.

Also look for and clean the main grounds on the vertical instrument panel braces located on either side of the climate control case

I've brought two badly misbehaving Delanair MkIII systems back to full operation by cleaning the grounds and connections.

Good idea on general principles, even if another concrete fault is found.

Cheers
DD

Here's what they look like......

Edited on 2013-03-25 14:57:44

Edited on 2013-03-25 14:57:10

It's possible one or both of the mode motor/gearboxes that drive the mode doors are stuck. Sometimes you can give them a rap to jar them free and maybe work for a while. They are circled in the picture. They won't be quite this easy to see, but a long screw driver can reach the upper one so you can give it a few good taps.

The fact it's blowing on the windscreen tells me there may be something wrong with the vacuum supply. The two gold vacuum actuators at the top left control some flaps. The one with the green hose should have vacuum on it to hold the defrost flap closed. The one with the black hose should have vacuum when it is requesting air conditioning, it opens the center face vent flap. So most of the time the green one should have vacuum applied.

Good luck!