e30 blower motor not working on any speed

[Boris3]

Put this up on R3v but maybe there are electrical gurus here that could weigh in.

1) my original post:

My heater/fan blower motor stopped working after a race weekend with too much time spent on rumbles and gators. My guess is I knocked something loose or broke something, the resistor or something else. I've got nothing on speeds 1-4, but with ignition on I'm getting power (12v+) to the blower switch (GN/BR wire). Started with the switch since I'll have to pull the strut bar and fire system hosing on top of everything else to get to the blower and was hoping for an easier fix.

Car is a 1990 325i. I've got the Electronic Troubleshooting Manual and have been following the System Diagnosis tests. YL to ground reads 0 as it should [since no AC switch]. What has me a bit confused is that I'm getting some voltage (around 5 volts) when I test the connections from the hot GN/BR wire to the other wires (YL, BK, GN, BU) at the blower switch connector where I should be getting 12. When the ETM talks about "voltage not present" does this mean 0 or just less than 12v? If the blower resistor was done should I be getting any voltage reading at all? Just want to know if there's something else I should be checking before I pull things to get to the resistor and the blower motor.

 

2) my latest: from a few minutes ago:

Finally got a chance to get back to this. I get 11.6 volt at fuse 20 with car in RUN. Battery voltage at the battery is 12.4 with car in off.

Replacing K7 relay with a new one makes no difference. Still get nothing at any blower speed.

Pulled the firewall cover and blower motor cover. Connections to the blower motor are fine, both power and ground connections are tight. Blower spins freely by hand. I pulled the resistor and all of the springs are fine. Safety switch looks a little corroded, so possibly the issue. Put it back in for now.

Just out of curiousity I tried car in RUN, blower on 4 = nothing. With everything still on I decided to check the connections with the multimeter at the blower motor with the blue and brown wire still connected to the motor and everything live. Touch positive to blue wire connector and negative to ground and the blower motor kicks on. Surprised me! Removed the multimeter leads and the blower motor keeps running. Will run on speed 4 and speed 3 but not on 2 or 1. Dies. When I try to go back to 3 or 4. Nothing. Blower motor will not work.

Repeated the above multimeter experiment again just to see if I could make this happen again and got exactly the same results. Runs on speed 4 and 3 and then dies on lower speeds or if I turn key to off and then turn key back to RUN. Blower motor will not run even when I go back to 4.

I was thinking replace the resister pack before the little experiment though this wouldn't explain why the blower motor wouldn't run on speed 4. Now I know that the motor obviously isn't dead.

Open to suggestions.

 

[B C]

Check to see if the fan speed switch is actually triggering the K7 relay. If not your problem lies between the switch and the relay

[Boris3]

Thanks for the suggestion. Just checked and fan speed switch is triggering the K7 relay.

[straight6pwr]

well that blows.

first thought: if manual jumping the motor makes it run, its just not getting power through the wiring. the odd on/off behavior with testing makes it sound like a weak connection somewhere.

i can tell you that you that of the two dead resistor packs (e30 and e34) that i've replaced neither one of them had visually broken springs. it seems dirt and/or corrosion in the terminals is also one way they stop working. maybe scuff/clean all of them? a little dielectric grease? i recall some guy saying he would pull out his resistor pack every couple years and clean it up to keep it running, in lieu of replacing it.

i have an e30 fan switch that you could borrow to test to eliminate the switch being a problem.

 

[Boris3]

Thanks. I figure the car is pissed at me for the latest track abuse.

Wondering if the connection issue is in the motor itself. I'm getting power to the switch and switch to motor.

Shot resistor or safety switch stuck open would explain the nothing on speeds 1-3.

What makes me think connection issue in the motor is the nothing on speed 4 (which bypasses the resister) unless I bridge the power and ground wires/tabs of the motor with the multimeter.

I'll try cleaning the resistor and see if that makes a difference.

[Boris3]

No difference scuffing the resister terminals. Pulled the wires off the motor and get just under 12v BU to BR. Looks like the connection issue is in the blower motor.

[Boris3]

Tried one more experiment. Tapping on the motor will get it to run for a bit at all speeds but I can see sparking inside the motor. So, my guess is something jarred loose inside the motor itself.

[straight6pwr]

aww well that sucks for the wallet, but at least you will be done with it.

[jc43089]

Brushes worn out in the motor?

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[Boris3]

Thanks. I thought about that as a possibility but in searching forums on this I don't think you can replace them on the e30.

[Boris3]

My mistake, looks like you can replace them

http://www.r3vlimited.com/board/showthread.php?t=348412

[jc43089]

They may not have a BMW replacement part but if you find one with similar dimensions. I've replaced them on an e32 blower motor, never an e30. I don't remember where I got them, maybe ace hardware. They weren't really meant to be replaced as in I had to bend some metal tabs I think and crimp the wire leads. It was a while ago though so I am not sure.

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[B C]

Yes, the hardware drawers at True Value have motor brushes

[Boris3]

Good deal, thanks for the info. Hoping to get time to pull the motor later this week and take a look to see if the brushes are the issue. 

[Boris3]

Pulled the motor. The brush is worn down to about 1/16" in the housing near the + connector side, and about 1/8" on the brush in the housing near the - connector side. The sparking I was seeing when I could get the motor to run by tapping the housing was around the housing at the + connector side. With the wear in the brush the braided copper brush wire is pretty low and may be coming into contact with things it shouldn't?  

[jc43089]

Yea they start much longer, excessive sparking is probably from it being so small that the connection is poor because the spring is not compressed much.

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[Boris3]

Plan B in case I screw up the brush repair this weekend or if it doesn't solve the problem (local Ace had the brushes for $4.40 each). Picked up a blower motor for $60 out of a 98 Z3 from a yard down in Kenosha this evening. Interchangeable with the e30.

[Boris3]

Nice when a backup isn't necessary.

Not the cleanest soldering job but it works

I just replaced the one brush that was sparking. The other one still had enough life left for a track car and I wanted to make sure that this was the problem. Reinstalled the motor and the blower works on all speeds.

Thanks again for the brush suggestion!

[straight6pwr]

very cool! nice tip on the z3 motor being swappable.

[jc43089]

Good deal! It's fun to repair things instead of just throw it out and spend money for a new one.

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