87 Accord alternator part 2

May 23, 2005 2 Replies
M

Alright, put in the new brushes, took the thing to the local shop... their machine said it was all good. Shoehorned it back into the car and fired it up...



I still get the charge light flickering, and the tach hovers around



7000-7500 although the engine isn't going that fast (actually around
2000-2500).

Am I missing some other critical component of the chargine system somewhere in this car? It's not the ALT fuse; that checks fine, and besides, it doubles with the fuel pump and the thing would run long at all if that was gone.



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S

at this point, id be checking all the wiring from the alt to the battery, as well as the battery, engine, and alt ground straps, if so equipped.

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M

Try looking around at idle with a DVM set on AC volts. Check across the battery, from the battery positive lead to engine, and battery positive to the chassis. They should all be less than .1 VAC (usually below .03 VAC). In fact, the battery negative, the engine and the chassis should be firmly connected together. If any of those readings are high, ensure there is a good connection among those parts. Then if the voltage from the battery positive to battery negative and engine ground look similar and high (above about 1/2 VAC), it still means bad alternator - normally, a diode. The absolute test is with a scope across those connections if you can get ahold of one; diodes or bad windings appear as negative spikes with two much smaller positive humps between them.

If you can't get any farther, the odds favor a bad alternator.

Mike

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