XJ discovery feature

I thought I has all the nuances of my 83 XJwuzza six a long rie ago.
It has been relatively dormant for a couple of years. Covid still here for me.
But, I do fire it up and let it run every few days.

The other day, the radio failed to play! It did light up. I left it that way and contmpleted.

No antenaa function? Nope it went up.

Fussed around the controls a bit.
voila, sound!!!

It has a mute fuction. Press in on the speaker balance cntrl!!!

I have had this car since 2001, Just learned of this function.

Now, my heater does not push warm air.

Check out the vacumn valve???


Some radios have annoying “hidden” features. Frustrating. Been there!

No heat:

Yes, the heater valve is a common failure. Broken or jammed. The actuator arm is external so you can see it move as you adjust the temp control from full cold to full hot. There’s always a chance that internal valve is broken away from the actuating arm, though.

No vacuum = valve open
Vacuum = valve closed

The valve should be open in all climate control modes except max cooling


Yes, Happy New Year Carl (and all).

As I understand it, the counterintuitive feature of requiring vacuum to keep the valve closed, rather than to open it when heat is called for, was implemented in later XJs to keep heater valves from getting frozen in the closed position when owners never used the heater (and thus never exercised the valve). This way, the valve is exercised everytime the car is started.

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Very interesting!

Actualy, tmy post was partly composed about a month ago. I rediscovvered it in te oen draft section!!

I figured out what to do to post t now!

MyPresent post is merely completing the od draft.

My heater vlve on the bujlkhead in the engie bay is a plastic replacement. No arm to indicte the open or closed position.
So, i am left to surmise

I guess I could remove the vacum line and plug it and thusly get heat and look into a fix in the spring!!


thanks for the input, it does make a type of sense, the type, jaguar is known for.

I recal our family 38 Dodge. A cable operated the valve. but, it could be shut down by a handle on the valve. Keepheat out of the cabin in summer.

Early on, i added a manual valve in the engine bay. Same “logic”.

Yes, I checked it! It is in the open position!

Thanks to each of you.


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