I’m sure this topic has been well discussed but I cannot seem to find a specific answer in the forums. My issue is when I change to defrost, floor, etc…no change in where heating air comes out. Full defrost and I get barely anything…still blows out floor vents and side dash vents. Both fans work, the car does heat up fine just cant get it to blow in the right spot (insert joke here). I found a factory reset action which I will try today but any other ideas?
Frozen blend flaps, there are servo motors on either side of the heater matrix box, when you adjust the heat pattern you should be able to hear them move (with the engine off) if there is no sound they will need to be unstuck.
If you remove both knee pads you can exercise them.
If I understand correctly…there are 2 motors on the passenger side and 1 on the drivers? I previously checked operation of the lower passenger side servo and blend door and they seemed to move fine. The upper I could not access due to not removing the glove box. Does the upper passenger side control defrost?, lower passenger side heater box, and drivers side controls what? Thanks for the response. Trying to unravel the heating puzzle…its cold in North Dakota.
No only one each side, they control the upper and lower blend flaps, the motor is one side and on the other side is a potentiometer, this feeds back the position of the blend flap to the computer
Happy Holidays Charles …
Here’s EVERYTHING you’ve ever wanted to know about the XJ40’s HVAC system …
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In my '94 MY car I noticed in the upper servo motor after I took it apart some years ago that the plastic gear that’s pressed onto the shaft has a missing tooth. It just broke off. I was able to rotate it 90 degrees so that broken part never gets in contact with the other smaller gear. Yes, it’s more difficult to get to the upper servo motor, it’s even harder for me because of the passenger airbag, that’s why I switched them around so the damaged one is the lower one now. So it’s worth to look into it if you can remove it. Although I still don’t get hot air but slightly warm but the cause could be the non closing flap(s) but I gotta take a closer look into it.
Grooveman, thanks for the delanair guide…will come in handy. I did the factory recommend reset but it didnt do anything. I did hear blend flaps moving but unsure if 2 or only 1 was moving. I also noticed when I turned on the A/C it blew out the dash vents and the defrost…and the floor vents blew hot air. My car is very confused. I’ll keep messing with it.
How do you Do It?
You may find some information in this thread from the archives which will help you in diagnosing what the problem is.