Lighting/wiring issue

[harmanrk]

Picked up a new HTT last month, and the dealer installed a 7 pin trailer harness. We have towed the trailer 7 times (3 trips + home from the dealer) At the end of this weekends camping, we hooked up as normal, however we could not get the brake or turn lights to work. When opening the door to the truck, the position lights, including the tail lights would come on for the 20 - 30 seconds that the lights stay on for. While testing this lights I was able to hear a 'hum' from the wheel area, whenever my wife had her foot on the brake which I assume is the electric brakes.

Short os having both the Left and Rigt turn signal lines having stopped on thesame trip. is there anything else that could cause this?

[handye9]

Glad to hear you found it. I don't think it is time to eat crow. Those electronic gremlins can do some strange things. You caught him. Next time won't be so easy.

[harmanrk]

Okay, Time to eat some crow.... Under hood fuse panel, #45. 25 Amp for TT turnsignals and brake lights. I never would have expected it to be a seperate circut.

Now I have to track down the correct replacment. I have a 25 amp mini in it, but he correct answer is a 25 amp low profile mini. Local stores stock them up to 20 amp. Need to browse DelCity, and pay more for shipping than the item cost.

[handye9]

From looking at other forums, Expedition has a second fuse box under the hood. There is a seperate fuse for trailer running lights. On one forum, someone said it was fuse number 20.

Check owners manual for the truck, or, look for a buse box under the hood (drivers side) and check those fuses.

The fuses on my F250 look like this. They come in various amp ratings, and, they are color coded. The one you are looking for is probably pink (20 amp).

[harmanrk]

handye9 wrote:

harmanrk wrote:
Okay, connecting 4 and 3 with a length of wire gave me running lights. 4 and 6 gave me the Right brake light, and 4 and 5 the Left brake light.

So it looks like an issue with the harness on the truck, with 5 and 6. Guess tomorrow I will be taking the truck back for them to fix. What fun.

Have you checked truck fuses?

The turn sigals and brake lights on the truck ,and work fine. I have not known of any where the wireing harness were on a seperate fuse. I know on the older truck I have experiance with, they were the same circut, as the flash rate of the signal would be effected by wether the trailer was hooked up or not. Unless they have stared using seperate circuts for the signals on the trailer the fuse if fine.

---Edited for thinking faster than I type---

[handye9]

harmanrk wrote:
Okay, connecting 4 and 3 with a length of wire gave me running lights. 4 and 6 gave me the Right brake light, and 4 and 5 the Left brake light.

So it looks like an issue with the harness on the truck, with 5 and 6. Guess tomorrow I will be taking the truck back for them to fix. What fun.

Have you checked truck fuses?

[harmanrk]

Okay, connecting 4 and 3 with a length of wire gave me running lights. 4 and 6 gave me the Right brake light, and 4 and 5 the Left brake light.

So it looks like an issue with the harness on the truck, with 5 and 6. Guess tomorrow I will be taking the truck back for them to fix. What fun.

[handye9]

Test trailer first. On the trailer (7 pin plug), use a flasher, fuse, or a piece of wire to jumper between the pins on each side of the notch out. This connects the trailer battery power to your running lights. Do a google search for "running lights in campground", to see drawings and decsriptions. If they light up, the problem is in the truck.


Check owners manual for the truck. Find and check the fuse for trailer running lights. It's probably in a fuse box under the hood.

Could also be, a loose connection in the harness or plug on the truck.

We had a poster just a few weeks ago, who had similar problem. An RV dealer had installed his 7 pin plug. He took the truck back to have them check the plug. They told him it was good. It really wasn't.

[Hondavalk]

As a general rule with 12DC acting weird, check for a good ground first.The hum does sound like normal electric brake noise.