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Brushes Posted by Ari [Email] (#2847) [Profile/Gallery] (more from Ari) on Wed, 19 Oct 2005 05:36:06 In Reply to: Battery Light - Help, 9000 Aero Owner, Tue, 18 Oct 2005 11:19:12 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The brushes are integral to the VR. If you just popped out the VR assembly and popped in a new one, then you replaced the brushes. It is possible to replace just the brushes, but it requires careful unsoldering and soldering. I suspect you would have noticed that.
Three possibilities come to mind-
(1) the VR is defective in that the brush springs are weak. As speed increases, the brushes get pushed away from the commutator, and the poor contact brings the light on.
(2) The commutator is badly worn. Very likely if the original brushes were badly worn. It's tough to wear just one side. If the commutator is badly worn/gouged, as the speed increases, the rough spots on the commutator bounce the brushes up (even with good springs), and the bad contact brings the light on.
(3) A bad/loose diode in the alternator. As the vibration increases with speed, one of the diodes is bouncing around.
The first two are hard to diagnose. The third is easy, with the right equipment. My recommendation is to bring the car to one of the many autoparts stores that will do in-car electrical system analysis. They'll hook an oscilloscope up to the electrical system, and they'll rev the engine. It will definately find a bad diode, and may show up weak springs/commutator. Unfortunately, there is no machine to show which side (brushes/commutator) is bad. So if it turns out not to be the diode, the best I can recommend is to pull the VR out and see if the brushes look gouged up. Then look into the alternator at the commutators (this would require the alternator to be out).
But I'd start with an autoparts store (Autozone, etc.) that will do a free diagnosis. Unless you have an oscilloscope at home.
posted by 192.249....
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