Hi All,

The heater blower on my A6 has abruptly stopped working. I pulled the motor out and checked it, runs fine, but replaced it anyway. Then I pulled the resistor pack thingy out and replaced that. Still not working. I've checked the earth to the stud in the passenger footwell, thats fine too.

So the problem is somewhere else. When I checked the voltage accross the motor, I only get about 8V, which I know isnt enough to spin the motor. What I really need is a wiring diagram. I've looked on the web and the only ones I can find show the resistor as a 4 terminal device. Mine is a 3 terminal device, with two big wires and one little wire, so presumably its big transistor of some type, not a resistor. It looks like this from the back, with round aluminium fins on the other side


I'd be really grateful if anybody could point me in the direction of a wiring diagram that features the above linked 3 terminal resistor / transistor thingy so that I might have some hope of debugging whats broken.

I'm desperately hoping its not the Thermotronic control unit, looks like a complete nightmare to remove, apart from anything else.

Thanks!