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Old Dec 21, 2005 | 11:54 AM
  #1  
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Dead Batteries

I have an 1989 F-350 w/7.3 diesel. If I let the truck set for several days without running it both batteries are drained. Won't even light interior lights. I have replaced both batteries and the alternater with the same results. Obviously I have a short somewhere! How can I find it? Could it be the voltage regulator? I noticed a note in the new alternater box which stated they recommend replacing the voltage reg when replacing the alt.
 
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Old Dec 21, 2005 | 01:15 PM
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There are several ways to find shorts, I think the best is to remove the positive battery cable, then connect an ammeter with a high enough range between the post and the cable (there are some meters that doesn't reguire to remove the cable), and write down the current. Turn off everything and disable the interior light that comes on when the door is open, then start pulling fuses one-by-one and check the current after each fuse, and put the fuse back if you see no change. When you see a significant change, you probably pulled the fuse for the circuit with the short in it.

If you pulled all fuses and saw no significant change, then the short is before the fuse box somewhere, and it could very well be the voltage regulator.
 
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Old Dec 21, 2005 | 02:52 PM
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Instead of hooking up a current meter in series, a test light will also work, and you don't have to be concerned with different current ranges.
 
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Old Dec 22, 2005 | 03:58 PM
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You can do it this way. And like the other poster said, watch out for that dome light messing the test up.

 
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Old Dec 27, 2005 | 06:40 AM
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Thanks for all the help! It was the voltage reg.
 
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