Heater Troubleshooting

[rils761]

hello everybody!
i am currently trying to figure exactly what is wrong with my heating system.
right now the switch does not seem to be doing anything, although i can feel warm air coming out of the vents once the car is warm and moving at a decent speed.
does this seem like the blower motor itself or possibly the switch?
any help would be greatly appreciated

[jbowen944]

Are you referring to the fan switch? If there’s no change at any of the speed settings, I’d check both the motor itself, and the resistor. What’s the year on your car?

[rils761]

It's a 1980. And yes I'm referring to the fan switch

[epmedia]

Make sure the blower spins freely. I'ts quite common for the bushings to get stiff, ie: in need of annual wd-40 service.

The brushes for the motor can also be sticky or worn out too, again - wd-40 if just sticky.

Easiest access by removing the cowling under the hood, assuming all other electrical checks good.

1980 e21 320i wire diagram, please save a copy! Link Here

[jbowen944]

If yours is the push on style of fan blade, consider a new motor. I went to rebuild mine, got new brushes, and the motor seized once again and actually burnt out the bush holders. The Bosch motor is only $63 with a lifetime warranty. Also if your fans are damaged in any way let me know, I’m working on replacement fans for these cars.

[I3MW]

I recently removed the fan and motor from my car. I thought I just had a bad connection, sometimes if I bent the wires coming on the motor it would temporarily turn off. Sorry to hijack, but after reading this thread I'm wondering if I should continue trying to track down the bad connection to a point with a multimeter or just replace the whole motor. Is there a smarter way of diagnosing these motors? Mine appears to be original.

[jbowen944]

Take leads from the battery or a known 12v source and connect to the motor. If it spins, you’re good there. If it doesn’t, new motor.

[I3MW]

It spins. but then I can move the wires such that it stops spinning. I think it's just a bad connection but I can quite track it down. What's the P/N on the bosch?