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Old Mar 29, 2009 | 05:50 PM
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Question battery light

Ok, on my way home from work.. truck (147k) started ok ran fine, halfway home battery light comes on. So i get home check out terminals and they are all green growing etc. I unhooked battery, cleaned terminals with baking soda/water mix, wire bruched them up nice and wire brushed terminals so no more green to be found. I put my charger on the right one and it read 80% so i let it go to 100. Then put it on the left one and it read 50 %. I let it charge to 100 %. I reconnected terminals, greased them up so not to corrode truck fired right up but battery light is still on. SO ... Do you think the alternator would go bad halfway home? Or maybe the left battery won't take a charge anymore from the truck. I bought both batteries from autozone (gold) May of 2006. So they are 3 years old. I am wondering if they are just junk batteries.. Cant Autozone check it out for ya right in the parking lot? or something like that. I guess i need to determine if the battery is bad or the alternator stopped charging. I suspect the battery because the right would have been low as well... any ideas? thanks Jeff
 
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Old Mar 29, 2009 | 06:00 PM
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Yea autozone can check it all out. Just went through that with my car last saturday. Sure does sound like the alternator. Can you start truck then pull battery terminals? If it stays running then alternator is working. Or use voltage gauge across the battery terminals. Should read 14.?. Around there, is what my alternator puts out.
 
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Old Mar 29, 2009 | 06:10 PM
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The alternator is the ONLY input to the light in your dash. The regulator controls it.

If the light is on, your alternator is bad.
 
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Old Mar 29, 2009 | 06:59 PM
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Ok thanks so i will be having my alt tested tommorrow night. Do you guys prefer the Ford Alt or get a autozone one etc. I can get the ford ones for 250 each. And Im not sure if i have 2 alt or not. I think I do then what is the correct amp alt to use? thanks Jeff.
 
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Old Mar 29, 2009 | 07:11 PM
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Yea, def the alternator. Autozone can test them but they tested mine on the truck and said it was good. Took it back a few days later to have them test it inside and they said it was bad. Bought a NEW one there and the light has yet to come back on...

I think the stock ones are 110amp. I paid right around 200 for a new alt at Autozone...lifetime warranty.
 
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Old Mar 29, 2009 | 07:34 PM
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yeah, had the same thing, also at 147,000 miles. My light just came on one day, and it was the alternator....I replaced both because the lower one had a cracked case, and the upper is the primary....
 
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Old Mar 29, 2009 | 07:46 PM
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Question

thanks, so here is one more question. If I have 2 the upper one is a Primary then what is the lower one. And how do I know which one is bad when tested? Do they both have to be replaced? or can just one go bad causing this to happen. Also are there any instructions on doing this change. I want to do the serpintine belt as well since it has never been changed thanks Jeff
 
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Old Mar 29, 2009 | 07:54 PM
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Ben will have to answer that one for ya! I dont have the dual setup...

Only thing I can think of is getting them both bench tested while off the truck.
 
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Old Mar 30, 2009 | 05:14 AM
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so here is a update, I plan on getting it tested tonight in my driveway with my brother. Anyway, on my way to work this am the light was off.. then half way to work (dark out lights on) the light came on. hen when i get here at slow speed idle mode the light went off, Looks light it only comes on when im going fast, Is the 2 alt setup one high speed and one for slow speed and idleing? maybe that tells me the primary one on top is the possible culprit? thanks jeff
 
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