Hi all,

My 02 XJR is producing no heat at low engine RPM. After 1500rpm and at 90F and using dash vent direction setting, heat comes out. If turning to AUTO setting at 90F and at 1500rpm, system reverts to cold air and RPM makes no difference. The higher the engine RPM, the hotter the air coming though the dash vents basically. Last night I drove the car 40miles at 70-80mph. Engine temp guage stayed in the middle so no obvious signs of engine overheating.

I topped up the coolant. No visible leaks, although I suspect there might be a leak. Level was at half tank when I topped up. Have had the car for six months. AC worked fine over the summer. I've read in various places about electric water pumps and air bubbles and fuses but any guidance on where to begin would be humbly appreciated.

Thanks!

 

My bet is the electric heater coolant pump.

bob

 

Thanks for responding. What makes you believe its the coolant pump?

 

The pump moves the coolant through the heater matrix

 

+1 on the heater pump as suggested by Motorcarman.

If cold at lower RPM's; pump.
If colder at higher RPM's, stuck heater matrix.
Only heat at display max. setting: sensor.

They tend to chew up their electric brushes, which can be replaced with some DIY.
Search this forum, there is at least one complete repair thread with pics if my memory serves well.