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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: mac on September 10, 2012, 12:16:17 PM
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Temp light started coming on in traffic the other day. I thought this was strange, because I had certainly been in hotter traffic in the past. I noticed I hadn't heard or felt the radiator fan come on, but I had earplugs in, and they tend to block that kind of frequency, plus, my horn still worked, and I seem to remember they're on the same fuse.
When I got home I idled the bike until the temp light came on, and peeked at the fan from the back of the bike. I could see it was turning, but not at anywhere near full speed, and as I watched, it was slowly winding down even more, until i could watch the blades go around. There was no "notchiness" whatsoever to this motion, so i have to believe nothing is stuck or seizing.
I'm ready to order another motor from beemerboneyard, but I'd like some confirmation from the experts that there's nothing simple left to check/fix that would save me from buying a new motor.
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Looks like you got a voltage drop somewhere in the circuit.
A common problem is melted brush holders.
Measure the voltage at the fan connector (with the fan running), to verify that it is the fan motor that is the problem.
Inge K.
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i'll bet it has a really high bit of friction--and it sure is seizing up, otherwise it would be running at full speed. It doesn't have bearings, it uses a cheesy bushing that rusts up over time, locks up the shaft and causes the brushes to melts the cheesy plastic housing. Been there, done that, got the t-shirt... Expensive sumbitch motors too considering how cheesy they are made.
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When I removed the old fan, I found that the spring holding one of the brushes to the commutator had somehow come loose. It was stuck to the permanent magnets in the housing. Bizarre.
I replaced the old motor with the new one I got from beemerboneyard, and re-attached the spring on the old motor which I saved as a spare.
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i'll bet it has a really high bit of friction--and it sure is seizing up, otherwise it would be running at full speed. It doesn't have bearings, it uses a cheesy bushing that rusts up over time, locks up the shaft and causes the brushes to melts the cheesy plastic housing. Been there, done that, got the t-shirt... Expensive sumbitch motors too considering how cheesy they are made.
It often makes me wonder how BMW can put such a piece of crap like those fan motors when they usually use such good equipment and have a good attitude to the extra bits they use.