3.2 Carrera Front blower speeds - how does the resistor work

[rft218]

Hi All,

I have been working on the blower for my 3.2 and am confused. I started with no cold air blower and took it all apart and found the motor had a melted area around the brushes so replaced that. This worked ok but I only have 1 speed - full speed. I then disassembled again and looked the resistor. I was expecting 2 resistors and a straight through earth to give the 3 speeds. It is like that but there is also a microswitch type contact underneath both resistors that is making a circuit and taking the resistors out of the circuit - see the green circled piece in the picture..

I assume it should some kind of thermal cut out but dont get why they are making a circuit when it is cold?. Does anyone have any ideas why it is like this ... or if it should be!

Thanks

Roger

[Jonny Hart]

The bimetallic contacts are apart when cold. When the low or medium speeds are selected, the resistor coils are used to drop the voltage, thus the fan turns slower. The air flow of the fan is used to cool the resistors.

So, if the fan fails to turn on a slow or medium speed, the coils will heat up causing the bimetallic contact to be made. This bypasses the resistor coil, forcing the fan to run on full speed. if the fan is broken or jammed, this is a better result than a resistor coil setting fire to the car.

We plan to remake this part as it is a very common failure. Contacts are usually stuck closed. Prize them apart and emory paper the contact surfaces.

[rft218]

Hi Jonny,

Thanks, that makes sense. They move freely so I will bend them up a bit so they dont make contact. Let me know if you remake these.

Cheers

Roger

[Magnum]

Hi Roger

I don't know if this is relevant but I've had the contacts on the fan switch (i.e. integrated into (and behind) the dashboard ventilation controls get so dirty that the fan only worked on full.

It may be worth taking the little dashboard ventilation control panel out to have a look and, if necessary, using some emery cloth on those contacts?

Regards

[rft218]

Hi Magnus,

Thanks, I am fairly sure that the contacts are ok but I will check also,

Cheers

Roger

[rft218]

success - bit gentle bending of the contacts and I have a 3 speed motor again!