Jaguar Repair: no heat, climate control system, vacuum hoses

Question
I have an 86 S3 XJ6. There is no heat coming out when I turn the dial to 85. The heater valve on the firewall stays down (closed?). if I disconnect the vac hose the valve opens (lever goes up)but still no heat. Also, when the fan is set to auto it just runs at high speed all the time. Note: It worked perfectly for about 20 minutes after I messed with the fuse then went back to no-heat mode.

Answer
Hi Ken,
The heating / AC system on the series III Jag is climate control system and is very complex system of vacuum and electronics. The only thing I can tell you to check is that both hoses on the heater control valve get hot or not to tell if the valve is really opening or not as that is a high failed item in the system. Also confirm that that both vacuum hoses are connected to the firewall down low next to the battery.
The system used door blending to control all of the heat and AC and the AC is on ALL the time that the heater is on to lower humidity in the car.
To do any diagnostic work on the system you need a manual and follow a step by step procedure. There is no way to cover it all by e-mail as I would have to write a book on it. Jaguar use to have an AC / Heat manual, check with the dealer.
Let me know,
Howard