Heater not reacting on heater knob

[joop911]

Hello all,
the the heater cannot be controlled anymore by the rotating heater-knob located inbetween the seats.
The heater is producing heat all the time (while it's almost summer here in holland!). I pulled the fuse of the heater control hoping that the heater would switch-off, but basicaly I have no idea how the system works. All manuals I have cover the years up to '85. I think my system is different.
Anyone knows were i start to look?
Thanks,
Joop

911 '89 3.2

[jester911]

One of two things. I think. First check the flappers on the heat exchangers under the car to see if the cable that controls them is still connected.

If that is okay then you need to open the console control housing the knob is on.
This will require removal of one of your seats. It has an access cover that pops off. If memory serves it may have one on both sides but I remember going in on the passenger side.
Anyway the dial itself has a little metal arm that may be disconnected to the mechanism.
Hopefully one of those two things.
Good luck.