So my A/C controls had been displaying symptoms of a malfunctioning amplifier. The car is basically stuck in defrost mode and won't activate any heating function in the winter. It is also stuck in fresh air mode, meaning in the winter I'm getting cold air inside the cabin.

I acquired a used, but warrantied amplifier and switched them out last night. No difference in operation.

The following are some of the things I noticed while I had the console sides disassembled, in case anyone has a suggestion or two:

1) Very clean, this car is. No signs in the dash of rust or corrosion (i.e., a failed heater core). No old antifreeze smell, no stickiness. This is probably the cleanest car behind the dash for its age I've ever seen. Coupled with its complete lack of rust/corrosion on the body, I'd say it was garaged all its life prior to me buying it. It's a Southern U.S. car.

2) There's a vacuum valve on the driver's (left) side of the trans tunnel, up by where the handbrake is. It has a rod that goes up in the dash somewhere. I can move this around freely; there is either no vacuum going to it, or it has failed. Not sure what this rod controls.

3) There are two wires with female bullet connectors on them; one wire is brown, the other is brown with a yellow stripe. They are disconnected and I cannot find anything that looks like it should plug into them.

4) On the passenger's (right) side of the car, there is a male end of a harness that comes out of the harness marked as "cigarette lighter" from the factory. My cigarette lighter works. But this plug is not plugged into anything. There appears to be a couple of male ends, a female end, and a dummy end (where two wires are combined behind it) on this plug. It is black and perfectly square. The wires are 1 large purple, 1 large black, 1 small black, and 2 wires red with a bright blue stripe. There was a piece of masking tape wrapped around the end of it, and someone had written "TAPED" on it (no kidding, thanks for the tip). Not sure what it goes to.

5) All vents are blowing air all the time. Dash, windscreen, tunnel vents, rear-seat controls, in all modes. But I also noticed there's a ton of air escaping behind the dash from somewhere high up in the dash. If you reach directly up from where the handbrake is, there's a ton of air coming from somewhere it shouldn't be. I'm guessing it's from either the center dash vent (which has the weakest flow of any vent) or the defroster vents.

6) Also, the air isn't as cold as I think it should be. But there is definitely a difference with the compressor off versus on, confirmed by disconnecting the compressor clutch.

It feels like I've got multiple problems going on here, but at least I've eliminated the amplifier as the problem (that, or I now own two malfunctioning amplifiers).

Jess

 

Are we still talking about the area behind the LH cheek panel?

Locate the pipes that go into the heater core.....roughly above the handbrake shaft. One of the pipes has a tab with a small, circular switch mounted to it. Are any wires attached? If not, your mystery wires probably go there.


Have you located and checked/replaced all four of the system fuses? Two in the Rh fuse box, one on the amplifier ground wire, and one on the brown/yellow wire clipped to the heater case, behind the RH cheek panel

Do you have the S57 wiring diagrams?

When you adjust the temp control do you hear a faint whirring? You should, but I'm betting you won't.

Cheers
DD

 

Doug,

Yes, still talking about the LH cheek panel on that one. I did not get all the way up to the area you're describing but I'll take a second look at that.



I checked the two ground wires on either side of the center tunnel; both looked good (i.e., not blown, but that's not a guarantee they're good). I have not checked the two in the RH fuse box.

I do not have the wiring diagrams, but I'll be honest: I'm not great at reading wiring diagrams or making sense of them. Yes, I know that's bad of me.

I do not hear any whirring when I adjust the temp control, nor does the little slider beneath the radio seem to do anything. I will note that I'm almost sure the slider beneath the radio did make a noise the very first time I used it after buying the car, but hasn't since.

Jess

 

No worries. It's not bad that you're not great at it.



Might be as simple as a blown fuse


Don't worry about that slider control at the moment. It's a very subtle trimming adjust that slightly changes upper-vs-lower outlet temps.

Cheers
DD

 

Jess:


All I can add is a comment on wiring diagrams. I am not good at them either.


But, the Jaguar S57 wire schematic is amazingly clear, best I've seen yet.


It has helped me immensely. I got a copy courtesy of a J-L lister.
I've shared pages via scanner with others.


Get one, now!!!


Carl

 

Update: All fuses seem to be functional.

Now the system only works when defrost is selected (i.e., won't work on low, auto or high). It's done this before.

Jess

 

This is something that you need to be sure about!

Defrost bypasses the 'auto control' part of the system.

It's beginning to sound like the servo has died but some tests with a voltmeter or test lamp are in order.

Or, if you wanna give it a whirl, the amplifier can be bypassed and the servo operated with jumper wires.

Also, what became of your two mystery wires? And, did you find the temp switch on the heater pipe? If so, were any wires attached?

Cheers
DD

 

Had a little bit of a family emergency today and wasn't able to do anything more than check the remaining 2 fuses I hadn't checked the other night. I probably won't get another shot for a couple of days now -- hence, why the 2 mystery wires will remain a mystery until I can drop the under-dash panel again.

When you say "sounds like the server has died," I begin thinking ominous thoughts. What's involved with fixing this?

Incidentally, I didn't just get a spare A/C amplifier recently - I also got what looks like either a relay panel or a connection panel as part of the deal. It's the part you see when you remove the LH console panel. Wires galore coming out of it.

Jess

 

Did you ever find out what these 2 wires with the female bullet connector behind the driver footwell panel go to? I have them there too, and the wires to the heater core pipe are connected. I also have a double unequal size male connector with a black piece of electrical tape over it, but the two don't mate up.

 

I have not done anything else with it. I'm in the process of looking for a shop to do the work for me. I called a shop I used to use in a different city before my most recent move and he said in his opinion, the whole dash was going to have to come out (to address the air leak from the ductwork) based on what he'd had to do in the past. Once he said that I threw the white flag.

Jess

 

Yeah, that's about right. Been there fixed that got the T-shirt.

If you're up for an adventure I can tell you how to fix that air leak behind the dash. As your ducts are in place you can probably do it in a day, 2 at the most.

However, you Will need to remove the crash roll and demister box from that side, plus drop the underskuttle for access. On the + side, the center duct connections are easiest of the 2 by far! In order to reinsert the duct on the fan (do NOT believe what the manual says!), you Must remove the fan from the car.

If you're still up for it, I can walk you through it. Success here is Incredibly gratifying and you'll Never have to do it Ever again!
(';')

 

I appreciate the offer but I'm well aware of when my (lack of) mechanical prowess is reaching its limit. I took a dash out of a 1975 Ford F-100 truck once and by the time I got it back in place I was almost about ready to take up motorcycle riding instead. I can't imagine this one is much easier.

We're also looking at the potential of whether we have issues with either the condensor or evaporator. Notes from the P.O. indicate they had a problem getting it cool a couple of years ago and replaced an expansion valve. When I got the car this past winter, it would blow ice cold, but I don't know how much of that was related to outside ambient temperatures and how much of it was actually due to freon. I'm going to get the whole thing done.

And then I get to do this all over again on my 89 XJS with the Delanair III system. Lucky me!

Jess

 

The plug / purple wire marked cig lighter is used in the Vanden Plas Edition of the XJ for the rear seat cig lighter, yov can ignore it if your car does not have a second cig lighter.