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new alternator and batteries but still alternator not working

Old 01-06-2012, 06:32 PM
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Join Date: Jan 2012
Posts: 1
Default new alternator and batteries but still alternator not working

I have a 2005 f350 lariat. They batteries kept dying so I had them and the alternator checked. Alternator was bad so I replaced it. It started but died again after just a few minutes. Got a replacement alternator and new batteries but still no charge to batteries. Dont know what is causing this problem any one have any ideas? I have read about blown fuses possibly being the problem,particularly the overdrive fuse
Old 01-06-2012, 07:26 PM
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Join Date: Aug 2011
Posts: 21


I dont think this will be your problem but since no one wrote, I figured I'd throw this out there. Since it happened to me.

I once installed a new alternator and forget to plug back in the wire that plugs/clips into the alternator (not sure of the correct name) But the batterty didn't charge and I soon realized these wires weren't plugged back in. Hopefully its something simple like this -- good luck
Old 11-10-2018, 06:54 AM
Join Date: Jul 2018
Posts: 84

Yes..f250 has a point. I would check that. When you do get it started disconnect the neg. battery cable and it should stay running just on the alt. That will tell you if your charging or just running off the battery..
Old 11-11-2018, 04:59 AM
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Join Date: Jun 2010
Posts: 9,252

Since the former posts were back in 2012 they are probably a forgotten matter.

There is something that should be mentioned here and that is NEVER disconnect the battery cable to confirm alternator function !!!!!!
If the alt is working and has no load it can self destruct. You were able to do that with a DC generator back then, but a NO-NO with alternators.
Old 12-13-2018, 08:56 AM
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Join Date: Jun 2010
Posts: 9,252

Usually when a vehicle is spec'd out , addl options are available such as higher output alternators.
They are equipped to supply the necessary power to operate the usual accessories and replace the power taken at the time the vehicle is started. To install a higher output alt costs more and may not be necessary so it ends there. The cable from the alt to the battery is the size the manuf chose according to anticipated loads. If you want to increase that output it could require a heavier gauge cable to handle that increased output, A lot will depend on what you plan to operate, since the majority of the time the alt may put out 100 + amps for a brief period of time and the original wiring will handle that. If you plan to have a heavy requirement for a lengthy period of time ,the alt will handle it , but the cable may not and become overheated and that's where the problems begin. If you have an alt rebuilder close by ,have them check what size cable is presently on your vehicle and from their experience if a heavier gauge cable might be necessary to accommodate the increased output over a longer period of time.
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