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1994 Ranger 4x4 Charging Problem

busterdarr

New Member
Joined
November 22, 2006
Messages
4
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City, State
Warren, PA
Year, Model & Trim Level
92 Explorer, 94 Ranger
My son has a 94 Ranger 3.0 V-6. The other night, it died. The obvious cause was a dead alternator. We replaced it, and it still wouldn't charge - fried the diodes in the new one, even with a fully charged battery. Replaced the alternator harness and instrument cluster, and it still fries the diodes in just seconds. We did find a short in the tail light harness, but I wouldn't think that would kill an alternator that quickly. We have new alternator #4, and I'm afraid to put it in, as the parts store won't replace it again. The truck will run and drive fine with the dead alternator and a charged battery - everything works. All the connections test as they should. I suspected a major short, but we keep coming up empty-handed. Any ideas? My next guess is to replace the Power Distribution Box and the Fuse Panel.
 



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Found something else out - if the alternator is NOT connected when you hook up the battery, the neg. terminal doesn't throw a spark. If the alternator is connected, the neg. terminal throws a pretty good spark when you hook it up. Checked for continuity from Power Dist. Box to the pos. batt. terminal and from Batt. lead on alternator harness to pos. terminal on battery, and both were good.
 












Checked out fine... gotta be a short, but only when the alternator harness is connected
 






If you haven't found the problem yet I believe I would pull all fuses and circuit breakers, connect the alternator and see if it draws the same arc when connecting the battery. I have found shorts in older vehicles that way, pulled all fuses, unplugged sections of wiring harnesses and put one back at a time. You shouldn't have much of a spark at all when connecting the negative terminal of the batttery. Be sure the doors are closed on the vehicle also as this will cause a small arc when installing the negative terminal. I would think something causing that much of a draw would also arc the fuse when it is reinstalled.

I thought I saw a post a while back where someone's fuel pump relay was sticking causing a sizeable arc and battery drain on their vehicle.
 






Problem solved

Ended up taking it to the Ford garage. Turns out the new harness came off a truck with an idiot light, and the harness is wired differently inside the covering, before it goes through the dash. It was throwing 24 volts through the stator. Well, I'm $213 smarter. Thanks for the suggestions.
 






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