battery light come on when accelerating

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Jul 31, 2009 | 02:27 PM

9902ford

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5th Wheeling

Joined: Dec 2004

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battery light come on when accelerating

Hello,

I have a 2002 Expedition with a 5.4 and around 70k miles on it. A few months ago the truck would start real hard and when started the dash panel gauges would reset. This would happen if the truck sat over night or sometime just sitting for a few hours. Also noticed that when accelerating to pass or under hard acceleration from a stop light the battery light would come on the dash and then go off. It had the original battery in it. Well the other day it would not start. So i put in a new battery. Then i took it down to the local parts store and had them test my alternator and it said it passed. Well it is still flashing the battery under acceleration but has no problem starting anymore. Any ideas, could the alternator still be going out?

Thank you

Jul 31, 2009 | 05:33 PM

cbradford

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From: Lost in Pa.

Yes the alternator could be going out and more likely a problem with the regulator which is part of the alternator (back of alternator).

Jul 31, 2009 | 09:25 PM

alloro

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I would first examine the belt and/or belt tensioner (much less expensive). If the belt is worn, or the tensioner isn't keeping the belt tight enough, the belt will slip. If the belt slips, the alternator output drops off and the light comes on.

Jul 31, 2009 | 11:31 PM

9902ford

Thread Starter

5th Wheeling

Joined: Dec 2004

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I will be taking a look at the belt. With a serpintine type of belt how do you sheck it for tightness? Also when the guy at the parts store checked the altenator it read 14.1 amps at 1500 rpm and 14.7 at idle. Usualy the battery light dosent come on until i accelerate hard like to pass when the rpms are much higher. Also will this harm my battery? It is still charging right?

Thank you

Aug 1, 2009 | 12:05 AM

MisterCMK

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From: Blue Hill Township

Assuming that your accessory drive components are in good shape, then your alternator is dying. Get it rebuilt or replaced.

Aug 1, 2009 | 02:40 PM

alloro

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Quote:

Originally Posted by 9902ford

With a serpentine type of belt how do you check it for tightness?

There is a wear indicator mark on the base of the belt tensioner.

Aug 5, 2009 | 02:10 AM

softie

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Joined: Jun 2009

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I had the same issue with my 01...... the light would come on when I got around 4k rpms then eventually 3k and then it just came one when I was driving at random. I ended up changing the alt and it was good as new