I have a 2000 Expedition. I am using the flat 4-Prong plug that was installed from the factory. About 2 years ago, I took it to the dealership and had the last 3 feet of wiring replaced. It is a seperate harness that is near the spare tire to the bumper where it is mounted. It was replaced just because the little cover tore off that keeps dust and bugs out of the connectors.
When I got it back, my trailer lights didn't work right. When you had your hazzards or turn signals on, the lights worked fine. If you hit the brake, the left one stopped. Took it back to the dealership, where of course they found nothing. Blamed it on my trailer, even though it worked fine on the other car, and fine before they replaced the wire. Well, after 3 trips to the dealership, I unpluged the harness and plugged it back in. Wha-Lah.. it worked.
Until now.
Now, if I have the trailer plugged in, the turn signals work, as long as the parking lights o brake lights are not on. What happend now? I have jumped wires trying to solve it, unhooked the ground from the harness and established a new one, I can't find any problems. All the lights work perfect as long as the are tested seperately. If you try and plug in a real tester, it fails. Think its the plug again?
I only launch is salt water but it has only been submerged once.. recently.. oh, like last weekend.
think the salt water could have damaged it?