Heating problem in Jaguar XJS

Hello, I have a problem with heating in the Jaguar XJS cabin, after turning the fan / fan turns on and nothing in the cabin heats up. I undressed the flap under the storage compartment and there are a lot of cables. I saw the ankle unfastened and I do not know what it is for ??

That connector is for the Econocruise Speed Control Unit DAC4293 for cruise control. It has nothing to do with your heat.

Does your heater control valve, located in the engine compartment in the center at the rear attached to the firewall, open when vacuum is applied to the nipple at the top and close when.vacuum is removed?

A stuck heater valve is a very common cause of heater problem in the XJ-S as is a clogged heater core. This is especially true for cars that have sat undriven for years, like yours has. There are lots of posts about heater problems in the archives.


ufff it is lucky … when I turn on the wheel / control button in the cabin, the fan at the front of the engine turns on strangely. So the heater valve is blocked, that is, you can not do anything about it / regenerate? is there any way do you need to buy a new one?

I hope that the attached pictures help to answer your questions.
The first picture shows the electric auxiliary cooling fan, located at the left front of the engine, circled in blue.

If this is the fan that came on this could be perfectly normal. In some years the auxiliary cooling fan is designed to come on whenever the climate control system is turned on to help cool the engine.
The next picture shows the heater control valve located at the rear of the engine at the firewall. It is hidden under some wires and difficult to see or work on without a flashlight…

The third picture show a heater control valve before I installed it showing the valve in the down or open position allowing hot coolant to flow to the heater core to heat the cabin.

The last picture shows the same new heater valve in the up or closed position stopping the flow of hot coolant to the heater core when full cooling is set on the climate control panel.

If you are not getting hot air from your heater after the engine is warmed up and your temperature gauge reads near the “N” on the gauge, it is possible that you heater control valve is stuck closed blocking off hot coolant to the heater core, or possibly your heater core is plugged up.

I recommend that you run your engine until the temperature is near the “N”, turn your climate control mode knob to “AUTO” and then observe your heater valve to see if it opens and closes as you move the temperature switch from full heat (85F) to full cool (65F) on the temperature set knob. You will need a flashlight to see the heater control valve. I find it is best to have an assistant turn the temperature knob while I observe the heater control valve.


Paweł, thank you for the big comment about the fan, I will be watching tomorrow. I still have a question about this fan in the cabin, can it be broken or is it not the reason that it does not give heat to the cabin ??? I will share the information tomorrow

The question is why this blower (in the photo) does not turn on? What could be the reason?

There are many reasons that a heater blower motor doesn’t work, especially in a car like yours that sat for 4 years.

The blower motor, the fuse, the wires, or the Air Conditioning Amplifier could all fail.

Do you know that there are two blower motors, one on the left side and one on the right side? Does just one not work or do both not work?

Try turning the key on with the battery connected and put the Mode Selector Switch on the right side of the console to the DEFROST position. Do either of the two heater blower motors work?


and this blower motor is on the left under the steering wheel (where does the driver keep his legs) ??

The two heater blower motors are located up inside the dash board and away from the driver’s and front passenger’s feet.


excellent thank you very much

Paweł, do you have any Jaguar XJS book information information? or website where can I find a description of Jaguar?


There are 5 documents that can be very helpful to you when you are working on your 1983 XJ-S coupe.

  1. Drivers Handbook, also called the Owner Manual, for your car’s model year.

  2. Jaguar XJ-S Repair Operations Manual (ROM)

  3. Jaguar Parts Catalogue that covers your model year

  4. Jaguar S-57 Electrical Guide for your model year

  5. Kirby Palm’s “Experience in a Book”

I was lucky and got a copy of the Drivers Handbook when I bought my car. I purchased hard copies of the documents 2, 3, 4 on eBay. You might be able to find a Drivers Handbook for your car on eBay as well. You can download Kirby Palm’s excellent book from Jag-Lovers for free using this link: http://www.jag-lovers.org/xj-s/book/Jaguar.html

I use all of these documents regularly when I work on my wife’s 1990 XJ-S convertible.

I have hard copies of these documents and do not use electronic versions. I know that some of these Jaguar documents have been made into digital format but I have read about many problems people have had with the electronic documents so I can’t help there.


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The early versions of the electronic documents were clunky. I was able to swap mine for later versions for XJS and XJR cars which are better, although still Windows centric. As far as I can tell, the ROM on the CD is a straight copy of the paper book. The parts manual is a copy of the microfiche that the dealer would use.

Having the electronic copy is great for printing out just the pages you want to work with, doesn’t matter if they get dirty, you can just throw them away. Not something you would want to do with a hard copy of the whole manual.

thank you for this book of Jaguar instructions, I looked and it is really nice and it will be useful.

I still have a question about the installation? because I had a bad radio connection and I saw the cable and I don’t know what it is from Don’t you know what he is for?


That cable is a grounding strap for the radio.


Thank you Paul_M_Novak for your next reply. I was wondering what a thick cable it is. I had a wrong radio installation and only played two speakers

If your replacement radio only worked on two speakers instead of four speakers like the original OEM Jaguar radio did it was probably installed incorrectly. I suppose that the other two speakers could have failed, the wires cut, or the radio failed internally. But those failures are less likely in my opinion than an improper installation.
Two of the documents that I already told you about have information on the correct way to wire the radio speakers, the Jaguar XJ-S Repair Operations Manual (ROM), and the XJ-S S57 Electrical Guide.


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