I bought this thing without testing the heat (it was August in Phoenix). Anyway, I've been reading all I can to diagnose the problem. I back flushed the heater core, it was clean. However, with the engine hot, only one of the three lines is hot. If I understand correctly, the top two go IN to the heater core, the bottom, large hose is coming OUT of the heater core. The weird thing is, only the BOTTOM one is hot! Am I wrong about the bottom one being the OUT? Any advice?

 

You may have one of three issues to sort through. 1. First determine that there is no air trapped in the coolant system. 2. In the engine compartment down low on the front passenger front of engine there is an electrical solenoid operated coolant diverter called the "dual climate control valve" (DCCV). This can fail and you'll not have proper heat or a/c control. 3. The climate control module (CCM) may have failed too. It is attached to the back of the climate control station on your dash. Check the many threads of this forum as a means to educate yourself on sorting through this issue. You'll do just fine.

 

I have replaced the DCCV (heater valve). Flushed the heater core - excellent, clear flow out of all three lines. All three lines get hot, but ice cold air blowing when I have the heat on. Everything else with the climate control system works fine. Just can't get any heat. If I take the #1 fuse out (for the heater valve), I can hear the valve either open or close, then I can hear it again when I re-insert the fuse. My temp guage never goes past normal. I am at a complete loss here. I don't think it could be thermostat, could it? Any ideas?

 

As bfsgross said, check the many threads. Chances now are you have a faulty sensor or the CCM (climate control module). (A dealer-type tool can test these or you might throw money at it by replacing parts.)

 

If you pull the panel on the drivers side of the dash there is a connector for the dccv. I think on your car its pins 11, and 12 on the conn that has only 3 wires. Useing a dvom you monitor for ground and voltage. At full heat you should see batt voltage cause the valve is normally open and you see volt. As you drop the temp on the ac panel you should see batt voltage go away and ground come up. This is what closes the valve. I have a module for your car but its a (001) suffix on the vcats label in your trunk. Let me know what you find.
you can also unplug the dccv electrical connector and the valve should open

 

Whoa Brutal...that was a good info. post, thank you.

 

Would you be so kind and elaborate on the exact panel location where the dccv connector is located?

 

Thanks to - JaguarClimateControl.com for the pic.

 

I do not know what MY car you have but this might help JagRepair.com - JDCCVSType

 

Thank you