Just bought a 1994 XJ6 VDP with 77,000 miles and am having issues with the footwell heat. I have read about the flaps sticking, or is it the grease in the motors causing issues? My issue is the fans work on all speeds but the heat to the feet works sometimes and sometime it just blows cold air. Is this a flap issue? Valve issue? Sticking motor? Bad HVAC control unit?

With my older Mercedes the HVAC control units are known to have their solder joints go bad over the years. I have solved the issue with rebuilt units from Programa in Florida but I don't see where they offer a rebuilt unit for the XJ40 Jags. Does anyone else rebuild/re-solder ours?

 

Hi MSGGrunt,

The first thing I would suggest is that you confirm your engine coolant level is full since low coolant can result in intermittent heat performance. So can the engine coolant thermostat if it is sticking open.

It very well could be a blend flap issue. Here are links to some photos of the blend flaps and actuators in our '93 XJ40. I'm sorry the photos at Jag-Lovers are so large. They lost the thumbnail links when they transferred the photos to their new servers. If you hold Ctrl or Cmd and hit the minus sign (-) the photos will be reduced in size, but so will the text.

Blend Flap Check & Adjustment - Part 1 of 5

Blend Flap Check & Adjustment - Part 2 of 5

Blend Flap Check & Adjustment - Part 3 of 5

Blend Flap Check & Adjustment - Part 4 of 5

Blend Flap Check & Adjustment - Part 5 of 5


Cheers,

Don

 

You can also view the images in normal size if you right-click on the photo and select "open image in new tab" (no text though).

Larry

 

Thanks Don, this is very helpful. Does the grease in the motors cause issues as it gets hard over the years? Can they be taken apart, cleaned and re-greased?

 

I haven't tried that but it may be possible. It can be done with the door latch actuator motors.

A common problem is that the foam weatherstrip-type insulation in the climate control unit deteriorates and the foam crumbs interfere with blend door movement (and also clog the evaporator core drip tray drains). The blend doors themselves can deteriorate and deform over time so they no longer move freely, and the connections between the actuators and blend doors can break. The defrost flaps are notorious for breaking at their inner ends, but can be repaired. It's all easier to access if you remove the dash, which isn't as hard as it sounds.

Cheers,

Don

 

Yes, the defrost flaps. Second time mine have broken, the flap falling into the Climate Control Unit and jamming the upper blend door in the cold position. So, heat to the feet, cold to the face vents and screen. Not optimal heading into winter.

Fortunately, a temporary "hack" can be used to restore heat and un-jam the upper blend door without removing very much at all. Basically you wiggle out the broken defrost flap out through the centre vent using a long pair of needle-nosed pliers.

First pry off the woodwork and take out the plastic diverter unit. Next, push on the vacuum operated centre vent flap and use something to temporarily hold it open. Using a flashlight, you'll see part of the flap jutting up at an angle. It's longer than the blend door so it can't disappear completely into the CCU.
Now, with patience, grab the visible part of the flap and move it to the one side until you can see an end. Grab that end and withdraw it out through the centre vent.

There are two vertical plastic struts at the centre vacuum door aperture -and in my case, I had to cut and remove one to get clearance to remove the flap. I planned to re-attach the strut later, but as it seemed to affect nothing I just left it that way.

These flaps are not part of the CCU but live inside the dash so in order to do a repair, the dash has to come out.

On the 94MY this is a little more complex because of the passenger side airbag. Still, it can be done without removing the steering wheel as the column can be dropped enough to get clearance. The dash is then removed sideways through the open passenger door.

Larry