electrical problem.....

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Jun 29, 2009 | 07:46 PM

r0n1n

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Mountain Pass

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electrical problem.....

i've been having what i thought were problems with the alternator, where the voltage needle bounces back and forth, i just replaced the alternator and i still have the problem. only now it just seems to bounce back and forth a little but the needle never dropped to the left like before. i used a test light and there is no short in any of the circuits. the battery before starting the truck was ~12.55 but now after driving back from checker, about 15 minutes, i turned the truck off and the battery voltage is 12.98

also, when i turn the ac to max the voltage needle stops bouncing and just stays in the middle. any ideas? i read somewhere that the gauge can lose it's damping???
thanks, jason

Jun 30, 2009 | 08:29 AM

Franklin2

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From: Virginia

At night with the lights on, if they blink with the voltage gauge, then you might have a problem with the charging system. If they are steady, but the gauge still varies, it might be the gauge.

Jun 30, 2009 | 10:04 AM

BPofMD

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From: Millersville, MD

Have you checked the electrolyte level in the battery (s)?

Jul 5, 2009 | 09:09 AM

r0n1n

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Mountain Pass

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at night the lights flicker when the gauge bounces,although i drove for 3 hours and when i stopped i tested the battery and the voltage was 12.7. so it is charging. the whole trip the gauge was bouncing back and forth.

Jul 5, 2009 | 11:46 AM

Franklin2

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From: Virginia

I don't know what year truck you have, but if you have the separate regulator system, run a ground wire from one of the regulator mounting bolts to the battery negative, and see if the problem goes away.

Jul 5, 2009 | 03:24 PM

r0n1n

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Mountain Pass

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sorry, 97 F250 w/ 7.5L it's an internal regulator, and i just got the alternator and reg replaced. the battery was bought in march 09, but i'll get it tested to see if there's a bad cell.

Jul 5, 2009 | 10:44 PM

Franklin2

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From: Virginia

Take a jumper cable and clamp one end to the alternator housing, and the other end to the battery neg. If that doesn't make it go away, I would check the plugs on the alternator to make sure they are not melted or corroded inside. If they are ok, I would get another alternator. You will not be the first to get a bad alternator if it's a rebuilt unit.