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Old 02-19-2012, 08:15 AM   #260 (permalink)
EcoModding Lurker
Join Date: Jan 2009
Location: Uk
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Car electrics are pretty simple and an alternator only needs three connections to work.

There is a large +12v wire connected directly from the battery +ve terminal which passes the charge to the battery, a small +12v feed which passes through the ignition switch and dashboard light and is used to excite the alternator windings and the Gnd, which is usually made by clamping the alternator to the engine, but sometimes there is a separate Gnd wire.

Some cars have a relay in the small +12v connection, but most dont.

If the three wires connections are good then the problem is the alternator itself, possibly a u/s regulator/brush pack.

You can buy a digital voltmeter for $5, which will be more than good enough for testing this and all other electrical items on your car.

I've read this thread all the way through and your mpg improvement is healthy and car looks great.
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