Alternator Troubleshooting
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Joined: Sep 2003
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From: SE, Michigan
Alternator Troubleshooting
Ok, heres my problem on my 82 F100. My last battery which was old would not show more than 12.25 volts. I replaced the alternator, voltage regulator, and put a brand new DieHard Gold battery in the truck. The brand new battery had 12.57 volts when I bought it. After starting the truck the battery was showing 12.37 volts. The truck starts fine and after you shut it off the battery goes back up to 12.57 volts. At my voltage regulator with the engine running I am getting 12.37 volts at output A. At output S im getting 11.85 volts. At output F im getting Zero volts. Output I has no function. With the key off A gets 12.37 volts. Outputs S and F get zero. Now my problem in guessing is that since im zero volts at F mean that I am not getting any current flow through my field. Any help? Thanks Fred
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Joined: Jan 2001
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From: Virginia
Take the "f" wire off the back of the alternator, and hook a short piece of wire to the "f" terminal in it's place. Start the truck, and while reading the battery voltage, touch the "f" terminal wire to the battery positive. The voltage should go way up, and you should hear the alt load down a little bit. This puts the alt in full charge mode, and should tell you if it's bad or not.
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