Heat starts out working then fails

XJ-S
21

Jeff,

Thanks very much for this–it’s a huge help! I went out and studied my engine today looking for what you describe. I see the connections you mention and agree that they will be the best places to disconnect.

One question: if I disconnect on the right side at the end of the coolant rail then the heater valve will be included in my loop, right? This doesn’t matter though as it’s open when the car is off I think? And then it gets vaccuum that keeps it closed until heat is asked for and available (based on engine being warm)? Or am I supposed to disconnect somewhere that won’t keep that valve in the loop?

Makes perfect sense regarding flushing procedure. Thanks for so much detail and helpful tips!

22

Douglas,

The heater valve is normally open so no harm is done leaving it in the loop. That being said, if you still have the steel version you may want to inspect/test it. They do rust up and fail quite commonly.

Good luck,

Jeff

1 Like
23

Douglas,
Actually, I’m pretty sure the Jaguar PDU was originally designed for pre-facelift cars.
The system was upgraded with software modules and connectors for later cars.
We used the system for my 94 but there were other connectors in the kit.