Hello all. Like so many around here, I am introducing myself and my truck by way of my problem.

Edited to add truck details: 99 F250 Super Duty, 7.3 PSD, Extended Cab, Short Bed.

I've had a series of electrical problems mainly involving the turn signals, parking lights, and hazards. I replaced the flasher and a few relays, fixed some bad grounds, and replaced bad fuses, and have arrived at one problem I can't seem to fix.

The most recent problem was that the parking lights and the dimmer light on the instrument panel would stay on even after all switches and the truck were turned off. I could get them to turn off by pulling the relay for the trailer tow park lamp/brake illumination. I could also pull fuse # 8 in the power distribution box under the hood and get them to go out. This fuse is for "trailer tow electronic brake illumination, park lamps, and trailer tow park lamp relay coil"

I looked at the two wiring harnesses and connectors above the spare tire, for the tail lights and trailer hookup, and found the remnant wires of some aftermarket crap that had been spliced in there. It is also almost certain that the previous owner submerged the trailer hookup launching a boat, if that makes any difference.

Cleaned everything up, redid the grounds for both harnesses, and now my parking lights turn on and off as they should, but the dimmer light in the instrument panel still stays on unless I pull fuse #8, mentioned above, or unplug the headlight switch. No other fuses affect it. I've blown this fuse several times, usually by accidentally creating a short to ground with a test light or moving wires.

Poking around under the dash, I've noticed that some of the wiring is messy. There are a bunch of ground wires spliced together from different harnesses, switches, etc. They all attach to good grounds (as far as I can tell) but I don't know if this would allow my instrument panel light to find its ground through some other circuit (like parking lights or trailer tow lights).

At one point in all of this my brake lights stopped working (turned out to be blown fuse #13 for the stop lamps, CHMSL, and trailer tow stop lamp). When I checked out my brake switch I found two hot wires going to it when there's only supposed to be one. The one that's not supposed to be hot runs into the back of the fuse panel.

Interestingly, I found another wire from the brake switch ran into a very weird splice. It included:

• this wire from the brake light switch, which was not hot
• three very thin wires (22 guage) that ran into a harness in the firewall (none of these were hot)
• one wire that came down from the instrument panel, that was hot when the dimmer light stayed on
• A large ground wire
• A wire that ran into the back of the fuse panel

I thought it was very strange that these wires would all just be mashed together and covered in heat shrink...especially with a ground wire that wasn't part of a harness, switch, relay or anything. I disconnected the battery, cut the ground wire, reconnected everything, and the dimmer light was still on. Touched the ground wire back together and blew fuse 8 again.

Also, now when I turn the ignition on without starting the truck, I get a nasty clicking/grinding sound out of my flasher relay. That's where I left off when I had to stop working on it for the day.

Based on everything I've read, it seems like it could be:

-Short to ground somewhere in the circuit with fuse 8 (park lamps, trailer tow brake lights, trailer tow park lamp relay), which could include the plugs back by the tail lights.

-Bad headlight switch

-Bad multi-function switch

Any ideas? advice? Should I clean up all of the grounds under the dash that are spliced together? What about the weird splice that includes wires from instrument panel, brake light switch, firewall, fuse panel, and ground?

I've been working on this for days...I just want to get to the point where that instrument panel light shuts off and I stop blowing the fuse for the parking/trailer lights. Thanks in advance.

 

Welcome, it seems as though you have been pretty thorough in your troubleshooting so far, at first glance I would say you have a 12V+ feeding likely the brown wire for the running lamps/dash lights. I do not have a schematic to look at the wiring with me right now, but My guess is that the trailer plug, 7-way at the rear of the truck is wired wrong, probably has the 12V feed to trailer hooked to the park lamps, at least that is where I would start looking. If it is a factory harness, you should be able to remove the pigtail for the trailer plug, to remove it from the circuit.

 

Thanks for the reply. That brown wire is hot all over the place, at the headlight switch, at the electric trailer brake plug, at the flasher. I just assumed it was supposed to be since I've seen some schematics showing circuits or parts of circuits that are "hot at all times." Also the brown wires from those three loads are spliced together (headlight switch, flasher, trailer brake plug)...I'm not sure if they're supposed to be or what.

When I get back to the truck tomorrow I'll undo the pig tail from that factory harness and see what happens. That was the harness that had aftermarket wires hanging off of it so it's very likely that the hack job they did back there caused most of these problems. Thanks again!

 

The brown wire should only be "hot" when the headlight switch is activated under normal situations, my guess is that you are backfeeding voltage into the wire from somewhere else. If it was the headlight switch unplugging the switch would eliminate it.

 

Are the prongs bent in trailer plug, Including the gooseneck hitch one if equipped? I saw something similar once caused by that. Does it have an aftermarket trailer brake controller and have u tried unplugging it?

 

Hey carltonwebb, thanks for joining the discussion. Just the other day I was reading one of your posts and had a laugh about the mileage you and your wife put on that Escape! I don't know if I've ever driven much over 3000 in a month.

When I first unplugged the trailer hookup it looked like one of the prongs was bent but I didn't pay much attention then so I'll have to double check which one. There's no gooseneck hookup, and right now I removed the trailer plug removed from the bumper and unplugged it from the wiring harness that goes up the frame.

There's no trailer brake control but there might have been at one time and it's possible that the prongs in the plug are also bent. I know one of the previous owners had a CB radio and a sub woofer installed under the front jumper seat/arm console, so who knows how much aftermarket stuff was on the truck before. There may have been an aftermarket alarm or remote start at one point but it's pretty obvious that some of the wiring connections under the dash are not original.

One wire is light blue with a red tracer, comes out of the headlight switch and then is spliced to two of the same color wire under the dash, but then I found one of these wires coming from the back of the fuse panel that was just cut and taped off. Didn't know if I should hook it into that splice or what.
Edited to add: looks like that light blue/red wire goes from the power window switches to the headlight switch, as well as from the power door lock switches to the instrument panel.

There were also aftermarket cab marker lights installed on the roof with a feed wire spliced in at the headlight switch, connected to the brown feed wire for the parking lights mentioned above by BigAl. I promptly disconnected that when I saw that a bunch of the light housings were cracked, 2 out of 5 lights didn't work and 1 only worked when I pushed down on it hard to force the ground to connect. Unfortunately, removing that circuit had no effect on anything.

Back at the trailer plug, I also recall removing a jumper that went from the brown wire in the tail light harness to a thin yellow wire from the vehicle wiring for the trailer plug (left turn wire I believe). It was spliced right by the harness.

Thanks again for the help. You guys are great!