Help me troubleshoot my heater/fan

[N-Gen]

Hey guys,

Yet another electrical problem, this one has been present ever since I've gotten the car so at no point was it working. It's completely dead! I tried every switch and rotor on the thing but nothing.

Power is being drawn, I had the glove box open and as I turned the power dial on the heater, the higher the fan speed the dimmer the bulb got. I have no clue where to start and I'd rather learn to troubleshoot the thing myself than just take it somewhere and be done with it :)

[spdracrm3]

blower fan

"Power is being drawn, I had the glove box open and as I turned the power dial on the heater, the higher the fan speed the dimmer the bulb got. I have no clue where to start and I'd rather learn to troubleshoot the thing myself than just take it somewhere and be done with it"

what do you mean by power is being drawn? what bulb? do you have a test light or DVOM? have you downloaded the correct ETM for the car from here http://wedophones.com/BMWManualsLead.htm ? diagram 6413-0 A/C blower controls and circuit description and troubleshooter on following pages....

if you have test equipment and tools i think the best place to access the wires to test is at the blower motor/resistor block under the cover in the engine compartment right behind engine ,the blower switch controls the positive voltage side, check for voltage or see if a test lamp lights on the 4 wires yellow,black ,green ,blue at the resistor or connector in each of the 4 speed positions , then check brown wire for continuity to ground , if you have voltage and ground at motor it may be stuck or bad , try spinning it by hand and it may start working , if not you need a new blower motor. if no voltage at motor check fuse , if fuse is ok could be a bad switch or the resistor pack might be bad but usually the fan works in high position only then.

[N-Gen]

I mean that every time the fan speed is increased the glove box light bulb gets dimmer. However I find this a bit odd, to be honest as I see there should be no relation between the two. Then again, I might be wrong.

I can test for voltage. Thanks for pointing out where the wires I need are located, I would have gone straight under the dash if I didn't know this :D

[jalopi]

Is the car running while you're doing this test? Or off? Because if it's off I could see a direct correlation between higher fan speeds and dimmer light bulbs.

[N-Gen]

Ah right, it was off...power is being drawn from the same source...damn I'm smart when I'm handed the answer! Lol, thanks Jalopi, completely overlooked that factor.

[jalopi]

Lol, no problem. On the upside though, it could be safe to assume that since your light bulbs are getting dimmer as you go through the switch range, you've probably got power going to the blower motor.... or somewhere. I'm gonna guess your switch/resistor pack is good and that you've got power going to them at the very least.

Either the power wires are grounding out somewhere between the switch/resistor and the motor (unlikely) or your motor is bad (more likely). However, this is just a speculation from halfway across the globe... you should definitely test to confirm!

[N-Gen]

Come to think of it, might that be the reason for my battery going flat quite rapidly when the car is sat in the garage? I've used different batteries with the same result.

[jalopi]

Maybe.... maybe not. Do a draw test and see what comes up.