Red dust on alternator

[MedMan]

Towards the end of September my alternator started behaving erratically. It charged correctly for 90% of the time but every so often the output dropped to zero for a few minutes before resuming again. (The ignition light warned me of a problem and the Battery Monitor confirmed what was going on) When I examined the alternator it was covered both inside and out with a very fine, reddish-brown dust. I removed the brushes (healthy) and cleaned a lot of the dust from them and from inside the casing where I could reach. I also cleaned the outside of the casing just to make myself feel as if I had done something. I put it all back together and it has worked perfectly ever since. Any ideas about what this red dust could be and where it has come from? I have had nasty, sticky black dust before from aging belts (I change them quickly if I find it) but this was not greasy, oily or sticky. Any ideas would be most welcome.

 

[Col]

Most likely is rust from the bearings, sounds like a replacement might be needed soon.

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[tr7v8]

I suspect the pulleys rust lightly when not used. A slightly out of tension belt then slips and rubs it off as fine dust. The fan on the front pulley then ensures that the dust ends up inside!

Jim
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[MedMan]

Thanks for your thoughts.

 

[dickh]

Could be 'fretting corrosion' from the bearings - they are moving slightly in their housing and rusting thereby causing the red dust. Only cure is to renew the bearings and possibly LOCTITE them in to prevent further movement.

dickh
I'd rather be sailing...