Just bought a cheapish XJR with a few gremlins. I found a blown fuse F8 in the luggage fuse box, apparently it's the Heater circuit water pump, what is this and is it critical as the car must of been running for awhile with out it. many thanks in advance.

 

I think the A/C clutch and heater pump run on the same fused circuit? (I might be thinking of the S-Type?)

Won't keep the car from running.

 

The air conditioning compressor on the X350 does not have a clutch as it is always engaged, but with variable output.
The heater circuit auxiliary pump ensures coolant flow through the heater even at low engine rpm.
Pete M

 

Thanks for your replies. So it's a auxiliary pump for the cars heater, not the main pump for the engine cooling, I guess if that was gone I would know about it pretty quick. I will keep an eye on how the cars heater performs and see if the fuse goes pop again.

 

It is 12 volt Bosch pump
https://www.ebay.com.au/itm/39405544...AaAoJuEALw_wcB

 

It is a pass through pump. In that the main pump does all of the work and pumps water through it and is just overrun until the RPM drop. It then can actually move fluid to the heater core, in a fairly small quantity, to keep passengers warm. It does not block any flow from the main pump.