my 2004 XJ blows great heat from the passenger side vents, but only blows luke warm from the drivers side vents. Now that its getting cold outside, it needs to be addressed. Is this a common problem? Will i most likely need to remove the heater box to find the problem?

 

Thanks for the quick response. This car doesn't have a heater control valve that i could find (i looked under the aux. water pump). What i ended up finding was a heater core that was half clogged with an orange gritty slime. the clogged portion extended into the drivers side of the heater box, while the free flowing portion was on the passenger side. Once i removed the glove box and the blower motor air box, it was fairly easy to replace.
This is a great forum! i hope this info can help someone else with a heat problem.

 

I’m sorry for the misunderstanding, it’s entirely my fault. I should have described the vehicle better. This is a 2004 Jaguar XJR supercharged 4.2. It has no dual heater control valve like, say an S-Type does (even with the same engine). The main difference is the type of heater core: the dual heater control valve system has three heater hoses going to the heater core. One for drivers side heat, one for passenger side heat, and a shared return line. It is essentially two heater cores in one. The non-dual heater control system has two heater hoses going to the heater core, one supply and one return. The dual zone temperature is controlled by blend door manipulation, not coolant flow.
Again, I’m sorry for the confusion. I know your time and knowledge are valuable and I appreciate you sharing a little of it with me.