Blown Running Light Fuses - Need Help!!!

[Sea Ray]

I keep blowing my vehicles (2005 Suburban) trailer running light fuse everytime I pull the boat out of the water. It is just the running lights, all the others work fine.

I am guessing I am getting water in a light or enough moisture to create a short but, I don't know what light the culprit is. The fuse will eventually work a few days later.

Last night when we pulled out there was only one light that look bad and we were 2 hours from home. I could not keep a fuse in there so I cut the wire to that light (figured better to lose one light then all of them). But that didn't help - I still kept blowing fuses.

Any ideas on how I can track the problem down. I do have a multi meter.

Thanks

 

[Silvertip]

Re: Blown Running Light Fuses - Need Help!!!

Disconnect the trailer lights before backing into the water. Water hits the hot bulb and the filament pops, somtimes creating a short inside the bulb. The problem lies somewhere in the brown wire between the trailer connector and each of the lights. The trick here is to first do a very careful visual check of the connector, and every point where the brown wire enters or leaves the trailer frame, every attachement point (support clips etc.) and then at each lamp. Next, remove all of the bulbs and then connect an ohm meter or test light between the brown wire terminal and ground terminal on the trailer light connector. Have someone pull, twist and wiggle the harness while watching the meter. If you don't get a short indication, the problem apparently lies at one of the lamps. Pull the lens from each and check the condition. As cheaply as some of the lamps are made, very often the brown wire has a frayed end that can contact a ground point inside the lamp.

 

[wire2]

Re: Blown Running Light Fuses - Need Help!!!

Typically a single run of 4 wires from the plug back through the tongue splits where the trailer rails go left and right. There will be connections there, hopefully done properly, and continue towards the wheel(s) area.

Since your problem is intermittent, it may take some patient looking.

If you pull all the running light lamps, is there any resistance between the brown wire and white, (ground)? It should read infinity.

Any muck or debris in a socket?

Any corrosion anywhere?

Any evidence of missing wire insulation, (mouse)?

You can test off the tow vehicle with a spare battery or a battery charger, + to brown wire, - to white/gnd.

When you find and fix it, I recommend a liberal layer of dielectric compound, silicone grease or Vaseline in all the sockets, then put the lamp back in. That keeps the water out and prevents corrosion on bare brass parts.

 

[kenmyfam]

Re: Blown Running Light Fuses - Need Help!!!

Are you unplugging the trailer electrics when you put the trailer in the water ???

 

[Sea Ray]

Re: Blown Running Light Fuses - Need Help!!!

Thanks for the replies. I am still not real sure where to start on this. As mentioned it is an intermitent problem. Last night some times the fuse would go as soon as I turned the headlights on and sometimes it would take a few miles????

I do not unplug the wires before entering the water. However, I will start to do that. But, I don't think that is the immediate issue??

I did try connnecting the tow vehicle to another trailer today and the fuse was fine. The tow vehicle and the second trailer both use a 7-pin round connector, the boat trailer uses an adapter for the four plug wiring harness.

Most of the wiring is inside the tubes of the boat trailer. It is an E-Z Loader trailer if that makes any difference? All of the lights seem to be sealed units, not sure if replacing a bulb is even an option (or I don't know how to get to them)

I can disconnect the wire plugs to the lights and test them there put I can't even keep a fuse in there long enough to test them!!!

 

[Silvertip]

Re: Blown Running Light Fuses - Need Help!!!

You may have an issue with the 7-pin to 4-flat adapter. My son in law had just such an issue with his.

 

[bjcsc]

Re: Blown Running Light Fuses - Need Help!!!

I agree with Silvertip. Not all vehicles are wired the same for their 7-ways. Check your vehicle 7-way flats for function with a meter to see what is where. Then check your adapter to see what is connected to each of the 4 positions on the 4-way side. Sometimes these adapters can be taken apart and switched up. Most often, it's the position of the electric brakes that cause the problem. None of the 4 trailers with 7-ways I have (2 horse and 2 FB) were wired to match my vehicles. I had to rewire all of them. I don't know how Chevys are wired, but Fords are wired like this, if your looking at the connector on the back of the truck:

1 o'clock: +
3 o'clock: RTurn
5 o'clock: Brakes
7 o'clock: GND
9 o'clock: LTurn
11 o'clock: Runn
Center Pin: Reverse

 

[SuperNova]

Re: Blown Running Light Fuses - Need Help!!!

Thanks for the replies. I am still not real sure where to start on this. As mentioned it is an intermitent problem. Last night some times the fuse would go as soon as I turned the headlights on and sometimes it would take a few miles????

If the brown wire is rubbing anywhere along it's travels through the trailer frame, you may have a high resistance short to ground that becomes a low resistance short when water hits it.

I do not unplug the wires before entering the water. However, I will start to do that. But, I don't think that is the immediate issue??

Even if you unplug the lights beforehand, the wire still gets wet and when you plug it back in after you pull the trailer out of the water, you'll most likely still blow the fuse.

I did try connnecting the tow vehicle to another trailer today and the fuse was fine. The tow vehicle and the second trailer both use a 7-pin round connector, the boat trailer uses an adapter for the four plug wiring harness.

Most of the wiring is inside the tubes of the boat trailer. It is an E-Z Loader trailer if that makes any difference? All of the lights seem to be sealed units, not sure if replacing a bulb is even an option (or I don't know how to get to them)

I can disconnect the wire plugs to the lights and test them there put I can't even keep a fuse in there long enough to test them!!!

The simplest way to start diagnosing this issue would be to check the brown wire on the trailer for resistance to ground (white wire or frame). The meter should read "O/L" for all measurements between brown and ground. Maybe dipping the trailer and testing will help find the problem.

Also, I am a little confused by your statements. In one statement you say you can't keep a fuse in there long enough to test it (which isn't needed, by the way) and in another you say you can't test it because it's an intermittent problem.

Either way the resistance measurements I am speaking of should be done with the trailer wiring disconnected from the tow vehicle.
--
Stan

 

[JAL51974]

Re: Blown Running Light Fuses - Need Help!!!

Even the sealed units go bad and leak...I had one last month that leaked, bulb shorted out and my fuse went out on the truck. Check those real good even Wesbar type sealed lamps fail occasionally.

 

[Sea Ray]

Re: Blown Running Light Fuses - Need Help!!!

OK, I had some time to play with the trailer and I found the problem and learned a few things along the way.

There is still resistance between all of the power wires (green, yellow and even brown) and the ground wire until you disconnect the bulbs, unplug the connectors and pull all the light assemblies off the frame that use it for a ground. The path for the power to return to the tow vehicle is through the ground wire (and the filaments of the bulbs) so there is a connection between the brown and ground wires.

In other words, simply checking for resistance between the brown and ground doesn't work until you remove all the grounds from the lights.

I learned that I was mistaken in the fact that the fuse only blew after the trailer was in the water. It might have been more likely but wasn't really related.

After disconnecting all the connectors I still had some resistance between the brown and ground wires. By pulling on the wires and watching how the meter reacted I found the spot where the short was. There was an area where the wire went through a hole in the tube at a tight 90 degree bend. It was rubbing on the edge of the hole and wore the sheathing off the wire. It was hidden behind a tube plug but once I removed the plug it was obviously the cause.

It is all up and running now . Thanks to all that offer assistance.

 

[kenmyfam]

Re: Blown Running Light Fuses - Need Help!!!

Glad things have worked out. Hope it stays that way.