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1978 corvette

by Patty
(Erie,Pa USA)

I have a 1978 corvette I put a new battery and alternator in it and it won't keep a charge can someone help me? Thanks

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Oct 18, 2010
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NO CHARGE *
by: Auto Appraiser * Ned

Hello, an alternator must first be fed by 12 volts before it can put out a charge.... when running usually 14.2 volts. check with a voltage meter the heavier red wire that runs to the backside of the alternator. (not the double plug wiring)***if it is live **has 12 volts or not? if it does not have 12 volts going to the alternator then that wire is bad somewhere along the way? this wire feeds the alternator 12 volts when you turn on your key....then start the vehicle and see how many volts it has ? charging more than 12 or not?
If no charging...take the alternator to an auto store and re-test it OFF the vehicle. Just because it is new...does not mean the internal voltage regulator is good? any spark of the wires while installing this alternator could blow the regulator with an electrical surge? therefore ruining the new alternator. let me know what happens if this works and can help diagnose from here? Thanks Auto Appraiser *Ned

Oct 13, 2010
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1978 vette
by: Patty

Thanks will do that..

Oct 13, 2010
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Pull fuses
by: Anonymous

You need to place an ammeter in line with the battery to positive cable and start pulling fuses. Once you find the circuit causing the discharge you will need to inspect all the wires that carry a charge at all times. This would be items that are not turned on with the key but are hot at all times. The alternator lead would be a good place to start. Just disconnect that and read the meter and see if it improved. You could have Diodes leaking!

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