Hello Group,

It's a 2007 XJ8L and the heater output is weak. Blower is fine, but the temp is far below
what it should be when commanded to max heat. AC is turned off.
I imagine something amiss with some kind of diverter door in a mixing plenum(??)

Any other ideas welcome

Thanks and Happy New Year...

Mike

 

I have the exact problem with my 2005 super v8. Its very frustrating now in the winter here in Norway.
So far i have changed the circulation pump and will test further.
I suspect clogged heater matrix or something wrong with the flap for fresh air

Does your car mainly blow cold from the facing vents in the dash? Does it gets colder when you are travelling fast?

 

It's not blowing cold, but just luke warm. I haven't noticed any difference with traveling speed.
Is the heater matrix easy to inspect?

Mike

 

Check the temperature difference on the tubes under the hood, at the engine bulkhead /by hand or pirometer/, if it's hot at the exit, You don't have a problem with the heater core and that's good news.
The bad news is that you have a problem with the flap motors, maybe only the one responsible for air mixing.

 

It is extremely common for the heater cores to clog on X-350s A chemical or compressed air boosted backward flush might clear it but be sure your tech is experienced and doesn't use too much pressure. Otherwise it's going to have to be swapped out. Not an expensive part or a terrible job..

Good Luck
Jeff

 

I had a similar situation on my '05 at 90K miles. Seems like I saw a photo on this forum of a heater matrix sawed open showing an extreme buildup on one side, where the air pushes through for the left (US driver's side). That explained the fact that returning water temp was fine, and right side dash vent air was much warmer than left side.

I was pursuing a replacement in the spring after a miserable winter, when the car was ruined in a flood and it all went to a junkyard.

 

I had the clogged heater matrix syndrome on the 2nd X350 I owned, (actually a 2007 X358). Replacing the matrix is not a hard job, and in my case was done by the main agent a mile up the road for not too much money. The parts were quite expensive, because Jaguar says that a fitting kit is needed as well as the matrix itself. Labour time is not too bad, but obviously being a main agent is high per hour.
First the glove box must be removed, then the heater control module and fan unit. The matrix is then exposed and extraction is quite easily done. Of course the coolant has to be drained. I would say it is a do-able DIY job. In my case the job was perfect with no leaks afterwards. Flushing is not recommended because it apparently rarely works, and if it doesn't, you've spent the money without result, so must spend more again to replace the matrix.

 

After som more fault searching I have concluded that Jaguar did a poor thing in winter testing theese cars.
Heater matrix works fine
Thermostat works fine, cars stays at 93c all the time

If i operate the heater manually (HI temp setting and manually adjust the fan) it gets really hot, but if I let the car adjust itself it will start to blow cold air from the facing vents on dash.
Recirculation works fine
No fault codes to be found

Does anyone know if Jaguar had a "cold climate" package for this car or if it possible to reprogram the logic for the climate control unit?
Its -18 here today and I can get the heater to work fine with manual adjustments.
In the summer everything works fine, and the temp inside stays at whatever you adjusted for, the fan is controlled very well (going to lower speeds when temp is reached