My heater stopped blowing warm air. The thermostat and water pump are good, and I'm getting excellent coolant circulation (both upper and lower radiator hose are hot). I'm thinking the heater core may be obstructed, but before I flush the core, I tested the heater pump operation (disassembled, cleaned, and reassembled) and the impellers spin strong when the heater control is set on Hi. I'm not sure of the heater valve though, as I tested for power at the connector and have none (with the engine on and hot). So the while heater pump is getting power and runs strong, I suspect the valve is not opening since I cannot confirm power at the valve lead connector. Can someone confirm if the heater valve has a relay or fuse and where it is located? And assuming the heater valve runs off the same fuse as the heater pump, why is the pump getting power while the valve is not?
Thanks in advance

 

I believe you can bypass the valve with some hose and verify if the core is flowing. When the valve is bypassed, you should instantly get heat. If no heat, then it's the core. If you get heat, then chase the valve.

 

Thanks for the suggestion, which makes sense. But I'm still puzzled why I don't show any volts at the connector which attaches to the valve. It's obviously an electrically operated valve - so shouldn't I have voltage in the connector line before it attaches to the heater valve receptacle, especially when the engine is on/hot and the heater pump is operational? I will bypass the hoses as last resort troubleshooting, but any idea on when (or if) the wire connector going into the valve should show voltage/current flow under "blower/heater on" conditions.

 

The Heater pump and the Valve share a common ground EM8R. The heater pump is powered through the Heater pump relay in the engine compartment fuse box. The heater pump relay is controlled by the airconditioning control module RW (red/white)
wire. The blue wire on the airconditioning control module controls the valve. If you bypass the valve and get heat, it is a valve problem as previously stated. You can also
see if the valve moves with the hoses disconnected.

You can search for parts on frugal mechanic. Amazon has a replacement for $339 with
shipping.
Frugal Mechanic - Auto Parts Comparison Shopping

This is a list of alternate part numbers.
Brand: OE Service
Part Number(s): W01331598456, W0133-1598456, W01331598456OES, R3020-64614, OES1598456
Description: OES Genuine Heater Valve; 1995-2002 Jaguar Vanden Plas; 2003 Jaguar Vanden Plas SC; 1995-1997 Jaguar XJR, L6 4.0L; 1998-2003 Jaguar XJR, V8 4.0L; 1995-1997 Jaguar XJ6, L6 4.0L; 1998-2003 Jaguar XJ8, V8 4.0L; 2000-2002 Jaguar XKR, V8 4.0L; 1997-2002 Jaguar Features: HVA..

Hope this helps a little.

 

DANG! For that price, I'd definitely be tearing that thing apart and seeing if I could get it working again. If not, wrecking yard.

 

Found one at a lower price.
www.prostreetonline.com $287 new.

Ebay has used for $50 to $100. Another number to try is Denso MNA6711AC.

You can always go with a mechanical shut off valve and just close it in the summer.