If there are problems with heat/air flow, chances are it's because one of the accurators sitting on the heater is broken.
It is 4 x accurators, which 3 are equal and one dissenting.
It is 1 behind instrument clustr, as I understand regulates the air between the floor and the windshield. Since it sits two servo on the right side of
heat pack, reachable behind the glove box, the bottom one handles regulation between cold and warm, and the upper regulating air between central air and
floor / defrost. These three accurators are equally fashiond, and keeps track of where in the regulation they are, using some kind of potentiometer,
conekted with the rotation.
then there is a accurator close to the fan motor, which handles switching between fresh air / recirculation, this accurator has no potentiometer,
so there must be some other way to know when the two positions are reached (do not how).
The 3 accurators sitting on the heat pack can be exchanged/replaced with each other without problems, just make sure the accurators are
adjusted to the zero position (arrow mark on the back). it is possible to put one of these also in the fourth place (but not vice versa)
The symptoms that some accurator is bad, is difficult to regulate air flow or heat, and that you usually hear a popping or grinding
sound behind the instrument panel when adjusting the heat.
Fortunately, these accurators are neither particularly expensive or difficult to change, but how do you know which accurators is broken?
A little rough, I think it is like this:
1. You can not adjust the hot/cold = lower accurator behind the glovebox
2. no central air or can not turn off the central air = upper accurator behind the glove box
3. no heating or no defrost = accurator behind the instrument cluster
4. no recirculation or no outdoor air = accurators at the fan motor