Next problem on my new to me 86 xj6 is the heat/cool .It seems to b stuck on high heat no matter what I put the temp dial on and where I put the hot to cold setting .

 

Lots of "could be" possibilities.

Might be as simple as the heater valve being stuck.

First, when you select "65" (max cooling) on the temp dial, does the system respond by switching air flow to the center vent? And, when select maximum heat, does the system respsond by switching air flow to the footwell outlets?

If the answer to both is "yes" then the system is understanding the requests and trying to comply. If the answer to either is "no" then we have to look at the control side of the system.

Anyhow, back to the heater valve......

Pull the vacuum hose of the heater valve and select maxium cooling. Wait a minute for the system to respsond. Now, put your thumb over the end of the vacuum hose. Is there vacuum? there should be. Vacuum *closes* the valve to cut-off hot water to the heater. If you DO have vacuum, reattach those hose to the valve. Does the valve operate? You can actually observe the external linkage moving (assuming it's an original type valve).

If the valve does not operate then it is stuck or broken





Are you referring to the slide control under the radio? If so, that's just a trimmer adjustment. Once the cabin temp has stabilized and the system is in "blend" mode the slide control is used to adjust the upper vs. lower outlet temps....so you can make the face level vents a tad cooler or warmer than the footwell outlets. It's a very subtle difference and has nothing to do with the overall heating or cooling of the cabin


Cheers
DD

 

hi there,
This is my first post here.I have an 88 XJ12 series 3. I have heater issues. I was trying to take the heater valve off, but after dropping the ratchet down the back gave up. I found actually the lever would move with a screwdriver, but there does n't seem to be any vacuumat the flexible. I'm not sure waht my next move is.There is hot air coming in on the drivers side vent, (LHD) and cool air on both footwell vents. It will demist hot too. There's not really cold air air coming in and nothing from the centre vents. also no temp change really. fan speed does n't change either.Could be the servo or vacuum system I suspect. Any ideas would be great.
Jonnyjag37

 

sounds like the Amplifier and/or the Speeds Relay. But I would replace the Heater Valve as suggested by Doug above; Start there. you have to watch the Heater Valve linkage moving as someone moves the TEMP switch up and down. (engine must be warmed up and running), If the heater valve linkage moves one way or the other, chances are the heater valve is good, and then you can move to the Amplifier or to the Speeds Relay.

 

Actually, to avoid confusion, you should start a new thread. Your '88 Ser III has the Delanair MkIII climate control (versus older MkII) and almost all of the operating systems and diagnostic checks are different. About the only thing this IS the same is the heater valve :-)

Or....

There are a couple active threads in the "XJS" section which might help, as the XJS used the same system from 1987-ish onward.

Cheers
DD

 

Hi Doug,
Thanks for replying so quickly. I will put a new thread on the XJS forum as I'm sure it has the Delanair 3 system.
Jonnyjag37