No running lights suddenly--and it's all my fault!

[MtnHaul]

Well shoot. Somehow a simple project has turned more complex for me. I was wiring in some new license plate lights and managed to kill my rear running lights. My truck is a 1992 F250 XLT 4x4 5 5spd 7.3 n/a. What I did was this:

1. Used a self-tapping screw to ground the license plate light to my steel flatbed.
2. Stripped away the coating from the wire that my old license plate light and rear running lights are powered by.
3. Connected the new license plate light to the same wire that powers all my rear running lights.
4. Turned on running lights and got nothing.

My headlights, front running lights, brake and turn signals work but no running lights in rear. Normally my stop/turn/tail lights plus my clearance markers will illuminate but I must have fried something. To make matters worse I don't even have a multimeter to diagnose/search for the problem. Hopefully this is just fuse related but I checked all the in-dash fuses and they look good. I am unfamiliar with the fuse box under the hood and really don't know what does what in there. i have to leave for work in the dark tomorrow and really need my running lights. Any help is greatly appreciated.

 

[direwulf23]

It's definitely worth checking the light switch box. I had a problem where my running lights quit working and it turned out my light switch had fried. Definitely worth a check

1994 Ford F250, 2wd, 7.3L IDI, NA, E4OD

2006 Ford Expedition Eddie Bauer, 2wd, 5.4L, automatic

 

[MtnHaul]

Well it was just a fuse in the under-hood fuse box, but the thing is I can't figure out why? I used a ground that I had just successfully used with a different light so I know the ground is making solid contact. I really have no idea why a little L.E.D. license plate light would cause the fuse to pop. I spliced several clearance/marker lights into my wiring and had zero problems. And all my rear lights, stop/tail/turn/clearance are LED and work flawlessly. The leads on the license plate light are not marked so I tried them both as ground or power with the same results. This one has me stumped.

 

[direwulf23]

An avoidance of electrical problems is why I like the IDI so much. Lol

1994 Ford F250, 2wd, 7.3L IDI, NA, E4OD

2006 Ford Expedition Eddie Bauer, 2wd, 5.4L, automatic

 

[MtnHaul]

Agreed. I appreciate and enjoy solving electrical issues--just as long as they are NOT on my truck

 

[direwulf23]

Indeed. The theory is intriguing but the practice not so much. At least the electronics isn't tied to the vital operations of the truck, except int the case of the E4OD

1994 Ford F250, 2wd, 7.3L IDI, NA, E4OD

2006 Ford Expedition Eddie Bauer, 2wd, 5.4L, automatic

 

[cpdenton]

Now that you have replaced the fuse...does everything work correctly?

You might have popped the fuse when you "tries the, both as ground or power." When you ground the wire that has power, you are going to blow the fuse.

Get a multimeter. You don't have to spend a lot of money to get one good enough for the work you are doing. It will make your life a LOT easier.

 

[MtnHaul]

Everything works correctly except for the new license plate lights. And yes a multimeter is next on my list of items to purchase.

 

[cpdenton]

Clean the wires really well. On the license plate harness, there should actually be a brown and a black wire. Brown is positive voltage in and black is the ground. This is according to the Electrical book.

If the rear parking lamps work, the brown wire should have 12 volts. They are on the same fuse and power wire.

 

[MtnHaul]

The previous owner installed the flatbed and did the wiring himself after cutting the harness at the end of the frame. The license plate harness is not connected anymore. What I find interesting is that there is a brown wire in the harness that seems to be for the running lights which is not being used. The PO instead grabbed power for the running lights by splicing into one of the wires he ran from the harness to the stop/turn/tail lights he installed.

I checked the instructions for the lights and they just say "connect one wire to ground and one wire to positive".

 

[IDIoit]

MTN, where are you from? i may have a complete tail light harness thats in my scrap pile.

 

[MtnHaul]

I'm near Santa Cruz.

 

[IDIoit]

East bay here. If ya want, I could ship them to ya. 15 bux total

 

[MtnHaul]

Figured out the issue with the lights--both wires got a bit pinched when I installed the light. I knew I probably shouldn't have used my impact driver to install an $8 plastic light.

 

[cpdenton]

There you go! Glad it was something simple. If you have any other questions with that hacked up harness, don't hesitate to ask.