'97 XLT Electrical Problem

[Beargap]

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

 

[wyochimneysweep]

pull fuses one by one till u find the circuit drawing the power down. then you will have narrowed it down

 

[Beargap]

pull fuses one by one till u find the circuit drawing the power down. then you will have narrowed it down

Thanks. 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 batery 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=

 

[budwich]

I would stick with the PDB as this is likely where your problem lies. Check the wiring going into the PDB cause if you blew a 20a there, its likely that something "large" moved thru your system and possibly "acred" out a wire or two.... especially if you are dropping your battery down.... you are looking at a "near ground" on a large cable "entry point" or close there after.

Also pull your trailer relays at the back as they "saw" the "ugly" also and may have melted to ground... .... having said that, they should be "blocked" by the blown fuse especially if it was / is removed.

 

[Beargap]

I would stick with the PDB as this is likely where your problem lies. Check the wiring going into the PDB cause if you blew a 20a there, its likely that something "large" moved thru your system and possibly "acred" out a wire or two.... especially if you are dropping your battery down.... you are looking at a "near ground" on a large cable "entry point" or close there after.

Also pull your trailer relays at the back as they "saw" the "ugly" also and may have melted to ground... .... having said that, they should be "blocked" by the blown fuse especially if it was / is removed.

I do appreciate the consult here...

I pulled the connector from the back of the PDB and still had the issue. So I pulled everything from the starter relay (wire to PDB, wire to charging system, wire to battery on one terminal, and also wire to starter motor on the other terminal) and STILL had the problem! So I reconected the PDB and charging system wires and jumpered between the battery and those two and all was OK (lights came on, batery stayed at 12v). Since a separate wire runs from the battery to the starter in addition the the wire from the starter relay, I suppose there is where the problem must be? That is the lead that is on an internal relay, it seems from the power distribution diagram, on the motor, which I canot seem to access from above (nor even see where it is). I suspect it is frozen closed, which would keep power on the starter all the time, but not enough to turn it over, I guess. Sounds like I have to get a new starter?

=Vic=

 

[budwich]

It would appear that you "blew" your starter and it just happen to coincide with your "meltdown" on the back.