vhenem Posted June 17, 2010 Share Posted June 17, 2010 It's a long one I'll apologize in advance :cheers: My license plate lights weren't working, so I crawled under the truck and noticed some wires that were not connected. So I did what any normal person would do and plugged them in thinking that was the problem, well it was........sort of. Jump forward a few days, I'm wiring up my electric fan to a switch so I can turn it on at will, get it working, go for a drive and discover that my dash lights were out, looked at the fuse box and sure enough, the park lamp fuse is blown, I replace it, turn on my headlights and pop goes another fuse. So I totally pull apart my fan wiring thinking that this was causing my fuse issues somehow, take it totally back to stock, turn on my headlights and pop, there goes another 10AMP park lamp fuse. So thinking back to my previous electrical earlier that week, I unplug both connectors I had plugged in, turn on my headlights and no pop, fuse is fine, go back plug in one connector, turn on headlights, and again fuse is fine. Plug in second, turn on headlights and pop goes the fuse. So I have these 2 Blue wires into one female bullet connector, and a single Black wire with a male bullet connector hanging out of the taillight harness, obviously they don't go together anyone have a clue as to what they are for ??? everything works without them plugged together. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted June 17, 2010 Share Posted June 17, 2010 License plate light connector Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 17, 2010 Share Posted June 17, 2010 Correct. The blue wire is the hot 12V supply to your license plate lamp; the black is the ground. Plugging them together is a direct short to ground (fuse blow) when you turn the parking lights on. Link to comment Share on other sites More sharing options...
vhenem Posted June 17, 2010 Author Share Posted June 17, 2010 License plate light connector Thats what I thought when I first found it unplugged, but the license plate lights both work. And the license plate light wire is Blue with a Red Trace Next :hmm: Link to comment Share on other sites More sharing options...
JeepcoMJ Posted June 17, 2010 Share Posted June 17, 2010 Nope, that is what it is for. Someone messed with your plate lights...they are spliced together somehow. Hornbrod is absolutely correct Link to comment Share on other sites More sharing options...
vhenem Posted June 17, 2010 Author Share Posted June 17, 2010 hmmm, on mine the license plate lights are connected to a single blue wire with a red stripe and the ground. The only thing that looks none factory is a section where I chopped out an exposed section of wire reconected it and then chucked some heat shrink tubing on it It's not that I don't believe you guys, but it really doesnt make sense couple things, the box is not original I'm not sure what year it's from, do later years have different wiring ? Mine came from the factory with the tow package, could this be a way to hook up lights for a trailer ? Thanks Link to comment Share on other sites More sharing options...
JeepcoMJ Posted June 17, 2010 Share Posted June 17, 2010 Mine actually has two sets of plugins for license plate lights...all 4 of them on my property do. Second set (spare) where your connectors are is also for plate lights for optional dealer install bumpers such as fey bumpers or similar, to power two seperately wired lights. There is no other factory intended purpose. Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 17, 2010 Share Posted June 17, 2010 Ah, why didn't you say that before? The blue wire (according to my FSM) is the connector you plug in the electric brakes on a trailer. Apply your brakes and see if you get a voltage. Link to comment Share on other sites More sharing options...
vhenem Posted June 18, 2010 Author Share Posted June 18, 2010 I answered my own question here I think, I had a friend send me some withing diagrams from Mitchell on Demand, it looks like in 88 (Mine) the wiring for the license plate lights were Dark Blue & Black In 91 they switched the wires to Dark Blue/Red and Black both diagrams show a single power lead though and neither one show this Blue two into one connector, well not that I can see anyway Link to comment Share on other sites More sharing options...
vhenem Posted June 18, 2010 Author Share Posted June 18, 2010 Ah, why didn't you say that before? The blue wire (according to my FSM) is the connector you plug in the electric brakes on a trailer. Apply your brakes and see if you get a voltage. Hmmm Ill give that a try when i get a second body here, it's kind of a stretch solo :D Link to comment Share on other sites More sharing options...
dasbulliwagen Posted June 18, 2010 Share Posted June 18, 2010 My truck also has two sets of plate wires, one for a single light setup for use with no bumper, and two more for dual lights on a step bumper. Theyve been unhooked for twenty some years, just leave them alone! Link to comment Share on other sites More sharing options...
Harper Posted June 18, 2010 Share Posted June 18, 2010 :agree: Leave 'em alone. The wiring diagram in the FSM for my '90 shows the wire to which you've referred....it's shown as a dark blue wire with a female bullet connector and is labeled "unused". It is spliced to the tail light circuit as are the license plate lights.The black wire, as hornbrod said, is a ground with a male bullet connector. Link to comment Share on other sites More sharing options...
Chukkklez Posted November 6, 2020 Share Posted November 6, 2020 Ok, so I should’ve read this whole thread before trying to wire in license plate lights because now I don’t have a taillight on that side.. smh lol But at least now I know why! I would still like to know which wires will actually give me license plate lights since I don’t have much time to trace down every wire myself. It’s is my daily and I drive home from work in the dark so any and all help would be super appreciated! Link to comment Share on other sites More sharing options...
derf Posted November 6, 2020 Share Posted November 6, 2020 The blue wire is the running lights. Tie that in to the license plate lights. Black is ground. Link to comment Share on other sites More sharing options...
Chukkklez Posted November 6, 2020 Share Posted November 6, 2020 I did and lost the taillight on that side. Might’ve just blown a fuse, maybe? 13 hours ago, derf said: The blue wire is the running lights. Tie that in to the license plate lights. Black is ground. Link to comment Share on other sites More sharing options...
derf Posted November 6, 2020 Share Posted November 6, 2020 Did you double check all of your grounds? Also, double check your splice. You need to keep the existing wires together and add the extra wire at the same time. Link to comment Share on other sites More sharing options...
Chukkklez Posted November 6, 2020 Share Posted November 6, 2020 2 hours ago, derf said: Did you double check all of your grounds? Also, double check your splice. You need to keep the existing wires together and add the extra wire at the same time. The lights I have are two wire LEDs and I spliced red to both blues on one side and then black to black of course. Now that’s the side the light is out on. It would make sense that it could be a ground issue. I’ll check my bases and get back. Thanks! Link to comment Share on other sites More sharing options...
Chukkklez Posted November 10, 2020 Share Posted November 10, 2020 I figured out my problem and it was a dumbass use error 🤦♂️ I cut the blue wires to splice in my license plate lights but the left side wouldn’t reach so I taped that side up so they didn’t make connection while not in use, thus cutting off the circuit to the rest of that wire. I fixed it and have taillights and license plate lights now. Thanks for all the help!! Link to comment Share on other sites More sharing options...
derf Posted November 10, 2020 Share Posted November 10, 2020 I've done worse. Glad you got it figured out. Link to comment Share on other sites More sharing options...
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