I have replaced the upper blend door motor once in the climate control system, and now it is exhibiting the symptoms of failure again - air comes from both floor and face vents and it doesn't change with moving the temperature knob, as it should.

This is a dash and airbags out job to do, so not a minor exercise. Last time I did this, I checked and the door seemed to move freely, but I'm wondering if it is binding to cause the second motor to fail? Or are the motors just junk?

If it is binding, there is an 87 XJ40 at the junkyard close to me, does anyone know if the basic heater box is the same dimensions and would fit in the car? I know the ECU is different but would the XJ40 box fit in the XJS? My car is a 94 V12. I can transfer over the wiring if the XJ40 box fits.

 

before you actually get into removal try a couple of raps with screwdriver handle or similar on the servo casing. Mine was playing up at one stage but this freed it up and it still operates correctly to this day.

 

That's easy enough to do! I'll give it a try.

 

The heater box is different, but most internals is the same.