RandyF150----

well i guess i'm crawling under the truck again. a pinched wire or something like that sounds the most logical.

i'll let you guys know what i find.

FYI, this doesn't sound like a clean fun way to spend a Tuesday evening

RandyF150----

OK..did some C.S.I work last night. i don't have the 12 battery charge circuit hooked up on my truck, the relay is NOT installed in the fuse block under the hood. it has to be added if you want the battery charge circuit to work. FYI- the battery charge circuit has no voltage i tested to make sure.
SO my 12 volts must be coming from the red wire (power feed) from the truck at the under dash wire wire plug/harness.

where does the power come from to feed the red wire to the trailer brake controller under dash harness? i'm SURE that where the short is My Chilton manual and owners manual do not show me that

i'm getting very close to the problem now.

R&TBabich

In a 2003 Expedition the RED 12AWG wire to the trailer electronic brake controller comes from 30A fuse #29 in the Central Junction Box and is hot at all times.
It's good to see a safety related signal like that has a dedicated line.
You originally stated the 12v was present on the brake activate line when the truck is running.
Is the 12v present all the time?

RandyF150----

sorry for confusion.

i'm am getting 12v at the blue, brake activate line with the truck running.
the red wire and blue wire on the under dash harness both have 12v with the truck running and NO brake controller installed. so i'm thinking the red and blue at the under dash harness are shorted together someplace and the wires going back to the 7 pin connector are OK (no shorts), because when the trucks running the only thing that has power on the 7 pin connector is the blue wire/ e. brake circuit.

this weekend i'll trace out the red wire that goes to fuse #29.

R&TBabich

Do you have 12v on the blue when the truck is not running?
The red is hot at all times from the fuse panel.
Fuse #29 may not be the correct fuse in a '99.
You're looking for a 30A fuse marked "Trailer electronic brake controller".

RandyF150----

I do not have 12v on the blue wire when the truck is off. i'm not sure about the red wire at the dash connector though.
i don't have any fuses or relays marked "trailer brake controller" i have a fuse for the electric trailer brakes and when i pull the fuse i still have power on my electric brake circuit (blue wire)

RandyF150----

I did some troubleshooting and this is what I've got. i'll spare all the little details and get to the issue

every time the fuel pump circuit is energized it powers the trailer brake feed wire (blue wire). not the red wire that provides power to the brake controller. ( the red wire that feeds the controller always has 12 volts truck on or off)
i pulled the fuel pump relay from the fuse/relay block and jumper-ed across the the contacts on the fuse block and every time the pump energized the blue wire that feeds the electric brake energizes. why??? i tested this with the truck not running and key removed, i tested this 10 times to verify what i was seeing. that explains why when the key is turned forward but not starting the truck i would see power at the blue wire for a split second, the fuel pump turns on to prime the system then off once primed. also with truck running i pulled fuel pump relay and lost 12v on my blue wire instantly.

i pulled the under hood fuse block and inspected every wire and terminal, i can not find anything wrong with them. BUT.. while i was moving wires and the fuse block around (with truck running) it would sometimes remove power from the blue wire and keep the truck running (fuel pump on) i would move things a little more then it would power it again. FYI -while doing this i did not have a trailer brake controller installed and i removed the 30amp fuse that feeds the e brake controller (red wire).

i have no idea how the blue trailer brake feed wire and the fuel pump circuit could ever be connected. and why moving the fuse block and wiring would cause it to work normal sometimes. currently the blue wire has no power on it and everything is normal, BUT i don't trust it. should i just pull a new brake feed wire and cap off the old one? i'm out of ideas

R&TBabich

Good troubleshooting.
The blue wire should be open ended at the brake controller connector and the 7-pin connector.
You certainly can run a new blue wire from the 7-pin to the brake controller connector.
I think I would do that, just to be sure.
It would be nice to find the connection to the fuel pump wiring so there isn't a future problem with that, but at this point ....
There is probably a section of harness underneath the truck where the blue wire is going back to the 7-pin and might be next to the PK/BK fuel pump power wire, but it makes no sense that moving the fuse block in the engine bay would result in any difference.

kd4gij

Look your wiring harness over good. Look for it touching or near the exhaust.

RandyF150----

I agree, i am a little worried about future wiring problems since i can't put my hands on the actual problem. i hate to kill the fuel pump because of this and be stranded along the road or up north on vacation.

the wiring harness that runs along the truck frame for the lights and fuel pump looks great and is not rubbing against anything no cuts dings dents melting spots. I've went through that harness a lot of times. it is the most obvious problem spot i would think. i could be missing the problem too.

last night i thought of something.......a couple of years ago i had a mouse build a nest under the dash board behind the vents. that being said... the blue wire at the dash board trailer control plug is bundled in with some other wires that run under the dash board above the vents to the passenger side dash. the fuel pump manual reset switch is located in that area too. this could be the problem! i have not looked at that side of the truck very closely i didn't think it was the problem area. i'll dig into that side of the truck next...maybe that will be it.

this is getting personal for me i really want to find this problem.