Jaguar Repair: jaguar, e mail system, heater control valve

Question
the heat is not working in my xj-6 jaguar? can you let me know what may be the problem

Answer
Hi Ken,
The heater control valve is on the firewall just behind the engine and is vacuum controlled. So all you have to do is turn the heat on and see if vacuum is applied to the valve and watch the valve to see if the lever moves.

The system has two fans and the vacuum controlled doors are controlled by a motorized rotor that operates vacuum valves to operate all of the vacuum doors. The AC system runs all the time the heat is on to take the humidity out of the air.

If the vacuum is not applied, you need to purchase the manual from Jaguar as it is too complex to cover via this e-mail system.

However, I have seen many heater systems quit working and it almost every time is the heater control valve rusts and locks up so just replacing the heater control valve when they are locked up usually fixes the problem.

All of this only applies to the XJ-6 up to 1987, if it is a later jag, I have no experience nor info on them.
Howard