Can an "External" problem affect an alternator?

Old 05-22-07, 07:50 AM
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Question Can an "External" problem affect an alternator?

Can a problem in the electrical system that is "external" from the alternator cause the alternator to generate an excessive voltage-output?. It's important to know that the volatge-regulator is "internal"-- the alternator/ regulator is comboned in one unit.

As best I know, this is a "feed-back" system. The "input" to the regulator "voltage-sensing" circuit is the output-voltage to the battery. The "output" from the voltage-sensing circuit is an "error-signal" to the " field voltage-control" circuit. If the "error signal" is indicating excessive output-voltage, the field voltage-control circuit of the regulator should reduce the magnetic flux of the rotating field-coil, resulting in a reduced output-voltage.

If this was a purely mechanical feed-back system, there would be a time-lag between "sensing" a deviation and correcting the "error", but with electronic components the responce time is instantaneous.

As best I know, the service shop has tried 2 or 3 alternators, but the problem , which seems to be intermitent, re-occurs. The warning-lites are illuminated, the engine hesistates when starting after a full-stop. Also, the needle on the temperature guage is affected.

Thanksto all who respond---
Old 05-22-07, 08:21 AM
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What vehicle is this? Sometimes, for one reason or another, people install a external voltage regulator when the alternator itself had one built in. This can cause some problems similar to what you are describing.
Old 05-22-07, 08:40 AM
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2 things come to mind, loose or bad connection somewhere, corrosion @ the battery terminal and don't forget if this vehicle had an aftermarket radio/cd installed, look there first for the connection (or wrong connecton). I'd also think about when it started, and what happened just before the problem occured...(Lt Columbo thought)..

Sometimes the only fix is a vehicle electric shop

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