97 Explorer electrical problem - Help!

I have a 1997 XLT 4dr, 4WD Explorer with 5-spd manual. It has been essentially trouble-free for almost 250K miles and we've routinely used it to haul a utility trailer. It came with trailer-prep, so when it was brand new I had picked up a Hopkins trailer adapter that plugged into the wiring harness under the left rear of the vehicle and everything always worked well. This past weekend we hauled my son's furniture home from college after graduation and the next day made several trips to a storage facility to store things. After the last trip, we smelled an electrical burn when pulling in the driveway and found the trailer wiring pigtail (from the hopkins "T" to the trailer plug) was fried. I unplugged it from the trailer and parked the trailer. The truck and all lights were working fine, so my son drove it on to work that evening and returned home afterwards. I had tried to pull the fried pigtail from the hopkins T, but it was stuck, and since my son needed to leave we just left it, thinking there was a short on the trailer somewhere.

Today we found the truck battery dead, really dead, like less than 2 volts. We tried jumping it, but the jumper cable got hot enough to melt the clamp insulation, so we pulled the battery and replaced it with a fresh battery. The replacement battery voltage dropped from 12v to 5 volts in a matter of seconds and, again, the truck wouldn't turn over. I removed the Hopkins T from the connector, but the same symptoms exist. No fuses have blown. I looked at the Auxiliary Relay Box #4 above and in front of the rear wiper fluid box, but none of the wiring is obviously stressed, and it is not obvious how to open, or drop, or otherwise get into the box to pull relays. Any ideas? This has me somewhat dismayed and alarmed at this point.

=Vic= Bear Gap, PA

Reply to
Vic Klein
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Follow-up to this problem...

While none of the instrument panel fuses were blown, I pulled all of the Maxi-Fuses in the Power Distrubution Box under the hood and found the 20a trailer tow fuse (#7) blown. However, even with ALL the Maxi-fuses pulled I still draw an arc and drop battery voltage to 9v or less as soon as it is hooked up. Is there a diode across the 12v system somewhere before the power distribution box?

=Vic=

Reply to
Vic Klein

My first guess would be the alternator.

Reply to
Tom Amundsen

If you haven't already done it I would disconnect the battery and check for a short to ground at the positive battery cable. If yes then disconnect the cable from the starter selenoid and see if it goes away. If not then disconnect the cable from the starter motor. If not then disconnect the red wire from the starter relay and keep going until you find the short. If it's not there then, like already suggested, check the alternator for a short. There are diodes in the alternator that could be shorted out and might account for battery drain.

Reply to
Ulysses

Thanks. I gradually disconnected everything from the starter solenoid and still had the voltage drop at the battery. Looking at the schematics, I saw that one line runs straight from the battery to a second solenoid contact in the starter. Dropping the line to the starter and jumpering to everything else on the starter solenoid, including everything on the power distribution box, showed the rest of the system was OK. I guess this is truly a coincidence, but it appears the starter failed (always connected to the battery) within a day of the trailer short. The truck is getting a new starter now.

=Vic=

Reply to
Vic Klein

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