Engine/Transmission (1998.5 - 2002) No power to: Trailer lights or dash charging socket

[John - K5AWO]

My '98 dually does not have power to the upper most 12 volt power outlet, the one that stays HOT all the time.

Also, the trailer marker/running light circuit has lost power to the 7 way trailer connector. This appears to be a factory harness.

I downloaded the manual and looked at the schematic on page 8W-54-2 and found what seems to be a relay operated by the headlamp switch on terminal C1/C134/S104/L7

The relay's contacts disappear into circuit L76/S319/L76

That is all well and good, I am an electronics technician (or used to be). I can't find the relay or the wiring bundle under the dash.

Behind the fuse panel are some relays, but they aren't marked and I can't find info telling which is what.

I am puzzled, did both of these circuits quit for the same reason (blown common fuse) or do I just have two separate items I didn't notice until now?

All of the fuses in the side access panel are good. Used my mechanic's light probe on each one. Found a 5 amp fuse that is turned on by the headlight switch, and it is marked "lamps"

Anyone home today? Being Memorial weekend, most of you are out fishing... .

Would sure love to just replace a fuse or relay, but if I can't fix it soon, it has to go to the shop.

 

[B.G. Smith]

I have a 99 FSM, it shows the auxilery power outlet in 8W-41-3 and to be located in PDC with a 20 amp fuse "L". Also shows the relay you mention shows to be for the trailer lights with tow package and is activated by headlight switch. Also look in PDC for fuse #8, 40 amp, should be for trailer tow power. Don't know if info from -99 is pertinent? By the way I went to school at Onapa (south of Checotah) bg

 

[John - K5AWO]

Thanks for the help.
Big problem for me was I didn't know where the PDC is or what it was.

I'm having a lot of memory issues since being slammed into a concrete wall by an 18 wheeler... . Things come back slow for me.

Found the PDC, and the trailer fuse, 40 amp is open;
also found the 20 amp fuse for the dash power outlet is blown also.

Now, I need to figure out why the trailer electric brake controller is not working. It don't even light up. Finally found the schematic for it and downloaded that today.

The monkeys who worked under the dash on this truck made a mess... going to take some sleuthing to trace things out. Lots of left over wire harnesses that go no where?? Not factory wiring either, so have no clue what is going on.