Alt Readings Drop... - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 01-22-2004, 09:07 AM Thread Starter
 
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Alt Readings Drop...

Wondering if this is normal behaviour for a '98 Full Size...

When I have the lights on, and then turn the fan on to full or just about full, the alternator meter shows a drop in voltage of about 2-4 volts. When I put my foot on the gas it goes back up, but I'm wondering if that's normal idle behaviour.

If not, time to get a new (read: better) alternator!
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post #2 of (permalink) Old 01-22-2004, 09:11 AM
 
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Re: Alt Readings Drop...

Do you have an electric fan and other goodies that will drain power? If so, its time for a new alternator. I replaced mine, and I have 14.5 volts currently... Mean green in my mind was a good pick except for the price
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post #3 of (permalink) Old 01-22-2004, 10:03 AM
 
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Re: Alt Readings Drop...

its normal to see a small drop at idle speed because the alt isnt spinning fast enough to generate the same amount of power thats being frawn. if mine dropped that significantly iwould be questioning the integrity of the alternator. my 96 with 135K miles never had problem one with the alternator.
your best bet is to head to autozone. they can test your alt and battery and they'll do it for free.
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post #4 of (permalink) Old 01-22-2004, 10:39 AM Thread Starter
 
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Re: Alt Readings Drop...

The truck is bone stock, so I know if I have to add anything I better upgrade. Better yet, it's still under extended warranty, so it might be covered if something is wrong with it.

But then again I was also planning on a Mean Green alt installation some time around, so if this one is not working to spec then it's time to get a new one!

Thanks much.
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post #5 of (permalink) Old 01-22-2004, 02:48 PM
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Re: Alt Readings Drop...

It sounds normal to me but if it is indeed bad I'd use the warranty and keep the new stocker for a spare or sell it for a couple bucks to help fund the mean green
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post #6 of (permalink) Old 01-22-2004, 07:43 PM
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Re: Alt Readings Drop...

How old is your battery? If its old then it might not be holding a good charge, so its putting more strain on your alt.
post #7 of (permalink) Old 01-23-2004, 08:36 AM Thread Starter
 
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Re: Alt Readings Drop...

Actually the battery is relatively new (three months, maybe?), and it's an Optima Red Top. I posted a while back that my battery cables got corroded and caused issues with the alarm. So I disabled the alarm (through the valet switch) because the dealer couldn't find anything wrong with it.

It was weird, as the alarm seemed to only go off after the battery incident and only at my condo complex at home! I was sitting there watching the damned thing and no one was messing with the truck.

I figure at least a little bit of a voltage drop, but it just seems a little more than normal. It's something I never noticed in my S-10 when I had it. I'll have the alt tested and trace all the wire leads to make sure something else isn't going funky.

Eventually I'm going to be adding more electrical (new stereo, amp, communication and off-road lights), so I don't want to get all this done to have the alt fry!
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post #8 of (permalink) Old 01-23-2004, 10:26 AM
 
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Re: Alt Readings Drop...

How’s your battery cables? I put on a new 140amp alternator on my truck then i noticed that the volt meter was still dropping when i would turn my turn signal on or have a lot of stuff running. So I decided to replace the battery cables with some heavy duty ones. The stock ones had seen better days. Had some neg and pos battery cables made out of 2/0 cable and #4 gauge aux leads. Put the new cables on and that fixed my problem. Heres the link to the guy i bought them from. Real nice guy and he makes some great cables.

http://www.custombatterycables.com/
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post #9 of (permalink) Old 01-23-2004, 11:21 AM Thread Starter
 
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Re: Alt Readings Drop...

Thanks for the link.

The cables are brand-spanking-new, but stock. They had to replace the positve, negative, wire to alt and probably something else after they were acid washed!

It's beginning to sound like normal behaviour to me, but I'm still going to have the alt checked. And then perhaps put in some electrical upgrades after the warranty runs out on me...
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