dugsud

My 83 SC fresh air blower has stopped working recently & I was looking for some help in fixing it.
I have removed the cover in the luggage compartment to allow access to the blower & tested the input with a multimeter. The problem is I'm not sure what the results mean.
When the main power plug is removed from the blower & tested I get 12V on one of the terminals weather the dashboard switch is on or off (ignition on) and I get about 6V on another terminal if the blower switch is turned on. I assume one of the other four is earth but I used the body to earth the multimeter.
When I put the tester across any two terminals of the actual blower I get an open circuit or continuity.
I think all this means the motor in faulty in the blower but I’m not sure.....any help would be appreciated.

DGaunt

Just went through this myself. I'll try to tell you as much as i learned in a way you can follow. Good luck!

first, when the ignition is on, the motor is always 'hot' and the ground is switched. In the hi position the neg side goes straight to ground. On medium and low, the ground goes through a resistor to slow the fan. This probably explains the 6V you are reading.

I also found out what pin does what. The most important is the pin closest to the passenger side and closest to the floor is the +12 pin. the others all go to ground, either directly or via the resistors as explained above.

I tested mine by running a direct wire to the +12 pin and then touching a ground to each of the other four pins in order to test them all.

This will confirm the status of the motor and resistors. If they are fine, look to the dash switch or the fuse. Of course check that the corresponding socket on the fan plug has 12V when the ignition key is in the 'run' position. Accessory will not energise it.

I am still waiting for someone to tell me the easy way to extract the ventilation controls from the dash if there is one.

Hope this helps. The key is understanding that is is the neg side of the circuit that is controlled, not the hot side. Also it is a single winding motor controlled w/resistors,not a multi-winding motor.

dugsud

Thanks Dave,
I'll have a look tomorrow & see if I can get any further.
It would be usefull if anyone knows how to remove the heater switch from the dash.
I can't see any way of getting it out without stripping half the dash!!

DGaunt

Well, like i said, it seems to be the worst documented part of the car....and nobody's talking here too. Well, keep in touch and maybe we can work it out together.