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Re: Signs of Failure Posted by Ari [Email] ![]() ![]() In Reply to: Signs of Failure, 96Aero, Wed, 2 Apr 2008 05:40:51 Members do not see ads below this line. - Help Keep This Site Online - Signup |
There are two kinds of alternator failures - electrical and mechanical.
Mechanical is pretty rare - bad bearings. You might hear that as a noise. More likely it'll have to be very bad to hear it. If you take off the serpentine belt and spin the alternator, and the bearings feel awful, the bearings are shot. Again, pretty rare.
Electrical is more common, and is usually a bad VR and/or worn brushes. The symptoms of worn brushes are numerous and can vary.
If you see the EDU voltage drop at higher rpm - can be a sign of short brushes bouncing at speed.
If the EDU readings have been dropping as of late. With the engine above idle, you should see voltages over 13.0 volts - mid 13's is nice. Again, above idle. If not, replace the VR. Remember, there is a lot of variation here - the voltage will drop when the alternator is hot (per design), it'll drop some if you put a lot of electrical loads on - A/C, blower motor, headlights and brake lights, and of course, low voltage at idle. But if the voltage doesn't come up over 13.0 at 2000 rpm or more, replace the VR.
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