Woo hoo! I'm the 1st 7 post :-) Intermittant a/c blower motor fixed

[gale]

My blower motor has been intermittant for the last couple years. I replaced the brushes in the motor but that only lasted for 6 months or so. Sometimes smacking the side of the console or hitting a pothole would get it running again. I finally narrowed the cause down to the sword after reading one of Max Fretter's posts on roadfly. Wiggling the connector got it running again, so I removed the sword & took the cover off the handle & inspected the connector solder joints on the pc board with a magnifying glass, & sure enough, 3 out of 5 solder joints had obvious cracks in them per typical BMW's outsourced piss poor soldering. After reflowing all 5 joints it's running all the time again:

http://www.nmia.com/~dgnrg/sword-01s.jpg

http://www.nmia.com/~dgnrg/sword-02s.jpg

Replaced the microfilter while I was that far into it:

http://www.nmia.com/~dgnrg/page_4.htm

[Bimmer Nut Ed]

Good job getting that blower to blow again.

Yeah, Im goiing to have to get some of my 7er projects on this board also. I jsut replaced the headlight lens. Which if you know what you're doing is like a 10 minute job. If not, an hour! So first lens, one hour, sencond 10 minutes for me! Figure I could save someone 50 minutes if I post it. Will do so soon.

[Bill R.]

bearings.. a couple of years ago...








My blower motor has been intermittant for the last couple years. I replaced the brushes in the motor but that only lasted for 6 months or so. Sometimes smacking the side of the console or hitting a pothole would get it running again. I finally narrowed the cause down to the sword after reading one of Max Fretter's posts on roadfly. Wiggling the connector got it running again, so I removed the sword & took the cover off the handle & inspected the connector solder joints on the pc board with a magnifying glass, & sure enough, 3 out of 5 solder joints had obvious cracks in them per typical BMW's outsourced piss poor soldering. After reflowing all 5 joints it's running all the time again:

http://www.nmia.com/~dgnrg/sword-01s.jpg (http://www.nmia.com/%7Edgnrg/sword-01s.jpg)

http://www.nmia.com/~dgnrg/sword-02s.jpg (http://www.nmia.com/%7Edgnrg/sword-02s.jpg)

Replaced the microfilter while I was that far into it:

http://www.nmia.com/~dgnrg/page_4.htm (http://www.nmia.com/%7Edgnrg/page_4.htm)

[gale]

Bill, that was some time ago on my old gutless e28 528e automatic, may it rest in pieces :p

Actually, I replaced the bearings in the blower motor 3 times, & they're not really made to be easily replaced. I kinda built an exoskeleton to make provision to mount a bearing, but they would wear out quickly. After the motor failed the 3rd time, nearly in flames & melted all the plastic brush holder business, I bit the bullet & bought a new blower motor for it.

On my e32, I merely replaced the brushes, can't say for certain now that that was really necessary, although it was probably worn brushes/dirty commutator that caused the circuit to draw more current, exasperating the sword solder joint failure, the wires were a bit warm last night when I was troubleshooting it.

Anyhow, the blower is running great today, seems much more robust, beyond the benefit of a new microfilter. I think more current is now being delivered to the motor vs. getting wasted producing heat at the sword pc board. What gets me is how the tiny copper traces on the pc board can handle the current without failing, they can't be but .040" or .050" wide & maybe .010" to .015" thick max.

[JonE]

Gale,
I have an intermittent problem with fan blower on my '90 535i. It was worse in the winter but always works when on high. When the other fan positions "cut out" there is a humming sound from the dash somewhere. I would often get less humming on lowest fan position. Were your symptoms similar or is this the dreaded MOSFET issue with the swords posted frequently? I am just wondering if the resolder would likely fix my problem too.

Jon

[gale]

Jon, Do you have discrete fan speed knob that ratchets into speed 1, 2, 3, 4, etc. for the blower speed knob or do you have the infinitely variable thumbwheel style like the e32 7's have? The latter would have the sword and the symptoms you describe are classical Mosfet failures in the sword. The ratcheting style as used in early to mid model e34's has what I believe they call the "resistor pack". I can't be certain it goes out as you describe, when it fails. Have you checked on Bruno's site (bmwe34.net)? I think he has a fair amount of info on the resistor pack replacement. I'm not even sure where the resistor pack is physically located in the car.

As for the buzzing, that's what they do when you turn it off. It's the stepper motors reinitializing themselves. If you have stepper motors, then you would have a sword and a thumbwheel in which case the failure you describe would be the Mosfet issue. Bruno has instructions for replacing them on his site as well. It's about a 50/50 crap shoot succeeding with the mosfet replacement. Rebuilt Programma swords run about $150 ea. + core at Eurasian, Zygmunts, BMA, etc. Might consider that.

gale

[JonE]

Gale,
Thanks for responding, my '90 535i likely has the sword, but I haven't taken the glove box out yet to check. The fan speed dial has detents for 1,2,3,4 fan speed but is actually infinately variable between the detents. Are the stepper motors you mentioned closing/resetting the vents after the car is shut off, cuz my humming sound is different than that, I can hear the "humming" immediately after fan position 1,2, or 3 intermittently "shut off"? The loudness will vary, but definately goes away when fan position is either off or on "4" (high). Probably is the MOSFET issue but was curious about your fix above and whether that might be the issue instead.
Jon

[shogun]

the stepper motors and the flaps which go into default position when you switch ignition on, and you hear the same sound after ignition off, sometimes for several minutes. That is normal.
Here a link to Johan's page, explaining the functions of each stepper motor.

click here (http://shrubbery.student.utwente.nl/johan/ihka/ihka.html)

[JonE]

Yah, I am familiar with the "buzzing" noises the stepper motors make when car is shut off. The "humming" noise I described above only happens when the car is running and I have the fan blower on position "2" and "3" mostly. The "humming" is intermittent and seems to come on only when the fan blower "cuts out", later if the fan blower cuts back in the "humming" is not there. The humming is almost like a loud vibration, very low pitched. It definately is resistor related, I think?