Help !!! Heater on my 2000 xj8 3.2 only blows cold. Blower fans work fine on heater and A/C. Engine temp gauge reads normal. Under bonnet I have the usual thermostat housing leak through the cap (the hex spanner fitting fills first) so replacement will be done shortly, hopefully with an ally one. Coolant level in header tank doesn't seem to be dropping excessively
Beneath the coolant header tank, on the leading edge, there is a small black plug with 2 pins but has nothing connected to it. Beneath this, hanging loose, is a brown coloured socket which I suspect should be connected to the black plug. However, someone (previous owner) has shorted out the 2 plug pin holders in this brown socket with a bare copper wire !! Has this socket/plug anything to do with heater water pump, or is it a coolant level sensor? How can I tell if water pump is actually working? Does it run whenever heater is turned on, or even continuously? The pump fuse is ok. Advice please somebody.

 

The heater booster pump and the temperature control valve are located back against the firewall (or whatever you folks over there call the panel at the rear of the engine compartment). If you have a plug and a socket which look like they should mate, but they aren't connected - try it. What can go wrong?

If you are new to this site, you should download the Jaguar electronic shop manual, called the JTIS. Look through the reference stickies or do a search on JTIS. Then read up on the heating and ventilation system and the cooling system. These cars require doing a certain amount of homework study.

 

Thank you Boomer. Will give it a try.Was worried it might start blowing fuses or worse.

 

Progress update. Removed the wire short and the "Coolant level low" warning came on. Connected the plug and socket mentioned, and the level warning went off. Looks like a previous user did the mod to disguise the loss of coolant over a period of time. Now I need to know if the pump works or has been disconnected in some way. Chucking it down with rain just now so that's for another day. Pity, if the sun comes out I won't need the heater. That's life I guess!!

 

Well, took it to local Jag dealer for a computer diagnostic test to find fault. They quoted me 1 hour labour, which I accepted. Turned out I was right. #3fuse in EM fuse box (engine bay) DOES control heater pump, although not listed as doing so in the handbook. This fuse was blown by security sounder having burnt out. Tech worked for nearly 3 hrs to find and fix fault and check system, still only charged 1 hr. Was well pleased. However, on way home it turned out that air conditioning was no longer blowing cold. So now have heater, but no chilled air, and the darned sun has come out !! I'll call them tomorrow, see if they can explain it.