I posted regarding this problem more than a year ago with no resolution so will try again. I have an '01 XJR with basically no heat. With the system calling for heat there is no power to the auxiliary circulating pump. Jumping 12 volts to the pump gives me instant heat. Fuse is fine. I plugged in a spare AC control module with no effect. The manual shows a possible source for insufficient heating is a seized in-car aspirator. The fan on my aspirator is working fine, but I'm wondering if the sensor could be faulty? The system seems to be regulating temp fine in the cooling mode so I doubt this is the problem but ... Is there a way to test the sensor, or can I bypass it by connecting the two leads and would this signal heat? Any help with this or other possible causes will be much appreciated.

 

Can you feel the pump running ?

The fluid flow from the pump goes through a water solenoid ( heater valve on page 68 and 69 ) that is not always opened or closed but is regulated by the A / C control module

You can tap on it to free it up in some cases

This valve does not rely on a relay reference lower left page 77 :

There is a relay and fuses for the heater pump in the form of # 15 / 10 amp engine compartment fuse box , # 3 / 10 amp engine compartment fuse box , and the relay control which is hot at all times at point 5 square

http://www.jagrepair.com/images/Auto.../jagxj2001.pdf

There is a Jaguar training guide # 703 that shows a on car self test on the A./ C control panel but the test does not always show everything

See page 110 :

http://www.jagrepair.com/images/Trai...des/703_SG.pdf

See also for the Denso system installed :

http://www.jagrepair.com/images/Auto...tem%201999.pdf

 

Water pump does spin regardless if the water valve is stuck or not. Wich one is missing from the pump ? Power or ground ? Is pump relay working ? Does climate control module turn the relay on ?

 

Thank you both for the info/questions. Pump has no power - ground appears to be constant regardless of system status (ignition on/off/calling for heat/not). My relays are buried in a waterproof box in the wheel well - will open up tomorrow and check relay function.

When space is tight

 

Woke up to a blown fuse on the pump circuit - replacement fuse remained intact but didn't solve the problem. Relay is fine. I checked resistance in the power feed from the relay to the pump and there was no continuity, so I suspect we have a break or short in the harness somewhere. Jumped that lead and we have heat:0) Since it's only about a 2' run from the fuse box to the pump I'll just install the jumper wire permanently and cut the harness lead. Thanks again Vauxi and Parker 2 for the help.

 

Hey Doug, would you mind sharing a couple pictures of the engine compartment? Having the abs module and fuse box hidden in the wheel well must make the engine bay look much cleaner.

 

Happy to share a couple of pictures. This wasn't about cleaning up the engine compartment but rather cramming an XJR drivetrain into an old Mark 2. Losing about 1000 lbs really makes the car scoot. I located the pump feed short where the harness passes over the shock tower tie bar - the harness is now tucked under the bar.

 

Whoa

 

That is SWEET!! Very nice!! 👏👏