Trailer lights blowing fuses in 97 F150

[92python]

I have been blowing a 20 amp fuse under the hood in my F150 when towing my boat. This has been an ongoing problem for a few years now. I blows and then the running lights and markers go out. The brake and turning signals still work. The truck has a connector that plugs into the round trailer connection that converts to the standard male plug.

I have a Warrior Trailer (Shorelander style roller trailer). I have had sections of the trailer wire replaced several times. The marina would show me the bad wire that had the sheathing wore off and exposed copper. That was making contact with the trailer and blowing the fuse.

This spring I brought the boat in to have a complete lighting job done. I asked them to replace everything from the plug back. For a couple months everything worked. Now I am back to blowing fuses. When I brought the boat back to the marina, everything worked fine, no fuse blew. They tried to tell me the problem is in the truck wiring. On the way home I blew a fuse.

Now I am back to blowing fuses. I put a fuse in and it held for 45 mintes of driving on Friday and Saturday then blew on Sunday AM.

Does anyone have any ideas or troubleshooting suggestions?

[gofishingtom]

friend has the same problem with his chevy truck 1999 same problem with the fuse under the hood had trailer all looked at and everything is fine must be something in the truck.. so far he hasnt figured it out either.. if anybody has solution please post

[wastewaterguru]

OK it can't be that hard.......

It doesn't short when the trailer lights aren't connected right?

So that eliminates the any of the "complicated" truck wiring with the exception of the trailer wiring which isn't complicated. Because you just had the trailer completely rewired and the same thing is happenning.....assume the trailer is fine. So now we've narrowed it down to the trucks trailer wiring and connectors.

You could rewire the whole back end of the truck in a couple hours and for about $40 in materials...........

Get someone that has a good multimeter and some basic electrical skills to check that the truck is wired properly. Maybe just replacing the trucks plug and adapter is the first step.......

It should't be very hard to find the problem.

[united jigsticker]

Hey, at least you're just blowing the fuse.

In our Chevy pick-up, if you shorted a wire it would blow out the ABS computer. Went through three or four of them, luckily it was under warranty, and the dealer never figured out why the computer was blowing.

The problem was, when we turned to make sharp turns, the extra wiring would pinch between the coupler bracket on the trailer and the bumper.

All fun and games.

Good luck.

[Guest]

I have the same truck, and I had the same problem 2 weeks ago. I was occassionally burning up fuses with only the tail lights on. The short created my brake and turn signal less bright and on both the right and left.

I found that in one of the rear lights on the trailer (inside the red plastic casing)there was a very small light bulb (night running light) that fell out of it's bracket and the positive/negative metal electrodes were touching. I had blown several fuses at $1 a piece before realizing what was happening. The wires near the problem got really warm, almost hot to the touch. See if you can isolate that.

I ended up bending the metal electrodes apart from one another and got rid of that little light bulb as it did no good anyway. Works perfect now.

It should be noted that my light bulbs on my trailer are submersible, and the light bulbs cannot be replaced without buying a new light assembly for $15 (and I don't have any dealers in my area to buy a new one). I broke out the plastic sealed shell to fix this problem and decided to unplug the lights before launching. Way easier and cheaper

If you have submersible lights, maybe try replacing both sides? That would have cured my problem. Good luck

[Dave]

My fuse use to blow on my F250 that way. It usually was when the trailer was in the water. I'm guessing since my boat trailer lens was cracked, maybe that was the problem. My brother's F150 blew some fuses as well. I don't know the source of trouble thou.
Note: I never blew a fuse pulling my ATV trailer so I have to credit the blown fuse to my boat trailer and water somehow.

[Guest]

Well, it's my turn to throw in my trailer light issue(s).

I have a 3200lb. Shorelander Roller w/surge brakes. I plugged the trailer into my connector on my '03 Suburban to see how it looked,everything, brakes, signals, clearance lights all worked fine.

Then, the next trip, I noticed I had lost the turn signals and brakes on the trailer, but not the truck, clearance lights still work, however.

Now, this weekend, I'm pulling away from the cabin, have clearance lights, 2 miles down the road I see nothing. I checked all connections, fuses on the truck are fine, as are all light functions on the truck.

This is clearly a trailer light/wiring issue--what's next--I'm not happy about the prospect of re-wiring the trailer. Is this a simple short, or?

Thanks!

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Chells

[Guest]

I always unplug my trailer lights at the ramp, Its just easier to unplug them than to try to troubleshoot problens in the dark along the roadside.

[vikes40for60]

""""Re: The problem was, when we turned to make sharp turns, the extra wiring would pinch between the coupler bracket on the trailer and the bumper.""""

American design and ingenuity at it's finest. Unbelievable that it would blow 3 ABS computers!!!!

Gander Mountain has a small Trailer Plug in tool. Basically you plug it in place of your trailer wires to see if voltage is running out of your plug. Turn your left signal on, look at the plug, you should see a light flashing. If not flashing on plug and is flashing on truck, your harness is bad. Use the same methodology for right signal, brake, and running lights. Takes the guess work out. Now thats a quality part, more than likely manufactured in Japan.

[This message has been edited by vikes40for60 (edited 06-02-2003).]

[92python]

Thanks for the info.

By bringing the boat in and getting the lights professionally done I was hoping for 2 or 3 years of piece of mind but I can see that isn't going to happen. I used to rewire my old boat trailer every couple years but with all of the marker lights on the new trailer I didn't want to deal with it. I probably should have skipped the markers and just ran new wires and lights myself.

I will try the trailer plug tester.

[Benny]

Chells, your problem sound simmular to mine this year.
Try sanding or polishing the ground pin on the plug in, both sides.
Mine was rusty up inside the female part so there was not enough ground to connect.The running lights worked till you hit the brakes, or turn signal.Even then the running lights were really dim.

92Python, if you stiil haven't figured the problem out , let me know and I will consult with my brother.He is a Ford Wrench out of Grand Rapids, MN. and my have hit this problem in the shop or out before.
Benny

[united jigsticker]

Most trailer lights now days are sealed and "submersable".

However, even if the lense is never removed, as with all things, age and weather takes its toll and makes these things leak eventually.

As Dave said, once the bulb gets wet...POOF, it blows.

However, the newer lighting systems aren't suppose to take the fuse of the vehicle with them.

My trailer is a 1996 with sealed submersable lenses.

I think I will start unplugging them now when I launch just as a precautionary measure. Nothing sucks worse then pulling out the boat at sunset and having the lights go out on the trailer...Unless of course you need to know how many they had in the slot...Right Dave?

Hope you get it figured out. Good luck.

[92python]

The thing is I already spen a bunch of cash getting the trailer re-wired and I think that the trailer still is the problem.

I can go out and spend the time and money to re-wire the truck too then tell the marina that the truck is fine and the trailer is the problem but the stinkin fuse won't blow until I have left the marina and am almost home. Funy how the fuse never blows when towing my utility trailer.

What will I wreck if I put in a 30 amp fuse instead of the 20?

[Dave]

I would NOT suggest putting in a larger amp fuse; that's not the fix. And, you could end up burning some wires.
I was looking at my '02 F250 and it looks like the trailer light plug is on an unpluggable harness. Maybe some wires got smushed back there, and short once in awhile ????

[Guest]

92python-
From what you described I can tell you that you have a short somewhere with your running lights only. You can narrow that down with those color coded wires. Double check that your trailer is wired properly since it has been re-done.

I would rule out your truck that has the problem if other trailers work fine.

Check all the connections again, turn on your parking lights and touch all the wires, all over and the connections. If they are warm just before blowing a fuse you are real close to finding the problem.

Do you have submersible lights? Take off the red lens on the back lights and see. I had a short inside the submersible lights that I could not detect until I broke the lens off to find the problem. The little bulb inside there (a running light) could have bumped off like mine did and created a short, and that constantly blew my fuses too.

[Guest]

Thanks everyone for the tips.

I also called Shorelander and one of the guys there gave me some tips on isolating problems which I'll try this weekend--checking the Ground, and the connections at the "Y" in the trailer frame.

I pulled 2-blown 15 amp fuses from the Suburban too which doesn't make me happy--it's from the boat trailer, my Flo Sled trailer doesn't do this stuff.

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Chells