Blown Truck Fuse ??

[Dodger1234]

I have a small trailer with the 4 prong plug. I have fixed grounding issues and I have even replaced the lights in the past. Now I have had for the first time ever a fuse blow in my truck for the running lights on the trailer. I have seen many posts regarding trailer lighting problems but it's usually the ground or a bad wire. I have never seen a post regarding the fuse blowing in the tow vehicle. Can the trailer cause this? If not then I'll take the truck in and see if they can source out the short.

Thanks Dodger1234

 

[GA_Boater]

Have you added any new lights?

I rented a U-Haul trailer once that had so many running lights that the truck fuse would blow when the lights were turned on. I think I bumped to amps up to 15 from 10 - It's been while.

 

[bruceb58]

Look for any places where the wires on the trailer may have rubbed through the insulation.

 

[Frank Acampora]

My S10 never had fuses for the trailer. When I shortened the truck on black ice I went out and bought a newer Silverado. I spent about 2 hours trouble shooting the signal lights on the trailer until I learned there was a 10 amp fuse for signals and a separate 10 amp for running lights. No shorts or other problems with the lights, the fuse just must have reached the end of its life. I went out and bought a 5 pack of 10 amp mini fuses, just in case.

Yes, there are several recent posts on this problem in this forum.

 

[bassman284]

Yeah, what bruce said. Last year I started blowing a brake/turn signal fuse on My Jeep. At first I thought it had something to do with putting it in the water until I got to a lake one day and my brother said it was out when I got there. I just went ahead and replaced the harness last spring.

I guess if I was really ambitious I could have pulled the harness and taped the bald spots, but I'm nowhere near that ambitious. A blown fuse is a pretty good indicator of a dead short - i.e. a bare wire caused by rubbing on the frame. Find the bare spot, tape it and you're good to go.

 

[Swoosh3]

As I learned from my dear Ol' Dad (RIP) was to disconnect the trailer plug as one of the pre-launch rituals.
Not sure if this has ever saved any troubles as I've just always done so.
Never had much for electrical issues on the boat trailer though.

 

[Dodger1234]

Thanks everyone. The current set of lights is 2 years old. My truck running lights are on a separate fuse from the turn/brake lights. Looks like I will have to look for a short on the trailer which will be cheaper than sending my truck in for testing of a short.

Well, being in Canada I have a few months to work on this issue. Thanks.

P.S. Swoosh3, many of us have learned some great knowledge from our fathers. Wishing you the best of memories of your father.

 

[gm280]

Thanks everyone. The current set of lights is 2 years old. My truck running lights are on a separate fuse from the turn/brake lights. Looks like I will have to look for a short on the trailer which will be cheaper than sending my truck in for testing of a short.

Well, being in Canada I have a few months to work on this issue. Thanks.

P.S. Swoosh3, many of us have learned some great knowledge from our fathers. Wishing you the best of memories of your father.

Dodger1234, it may not be an actual short but more of a corroded connection drawing more current. So if you can't fine a direct short, try cleaning all the connections and the bulb inserts. JMHO!

 

[bruceb58]

Dodger1234, it may not be an actual short but more of a corroded connection drawing more current. So if you can't fine a direct short, try cleaning all the connections and the bulb inserts. JMHO!

Corroded connections cause less current to be drawn.

 

[gm280]

Corroded connections cause less current to be drawn.

Not if the corrosion is parallel with the actual connection. Like a plug in double filament bulb that also has some corrosion from the base to the terminals. Then the current has more then one path for it to take and the current increases. A high resistance path but a path none the less. And I've seen lots of such conditions in such setups when water is involved. JMHO!

 

[bruceb58]

Then that may be possible.

There are some people that thing corroded connections will cause more current to flow which is impossible.

 

[gm280]

Then that may be possible.

There are some people that thing corroded connections will cause more current to flow which is impossible.

I totally agree bruceb, If the corrosion is between the end terminal of the bulb and the connection point, then it actually inserts a high resistance connection. And of course as you know the higher the resistance the lower the current.

 

[Scott Danforth]

entirely plausible

my old durango would blow the running light fuses in moist weather. road-salt got up into the trailer wiring harness tee-connector, and would short out the circuit when it was wet out. a new Hopkins wiring harness for the truck cured that issue.

my new trailer originally had a very unique wiring job by the prior owner and would short out both the brake light circuit breaker and the running light fuses. a 100' spool of 4-conductor trailer wire and new lights cured that issue.

if the light housings have water in them, they can blow a fuse.

 

[Dodger1234]

Looks like I may be doing some rewiring this winter.

Dodger1234

 

[bassman284]

Thanks everyone. The current set of lights is 2 years old. My truck running lights are on a separate fuse from the turn/brake lights. Looks like I will have to look for a short on the trailer which will be cheaper than sending my truck in for testing of a short.

Well, being in Canada I have a few months to work on this issue. Thanks.

P.S. Swoosh3, many of us have learned some great knowledge from our fathers. Wishing you the best of memories of your father.

It might be helpful if I clarify my deal with this. The left side blew twice, once in May and once in July and then never blew again. In late September the right side started blowing every time out. Season was about over so I quit replacing the fuse after about the 4th time.. The next spring I had the whole harness replaced.

The thing about mine was, you couldn't detect the short when the trailer was sitting still, it only blew when it was moving. When I got the old harness back I found the worn spots. They were very small and a little hard to spot. They were also about 3 feet forward of the rear lights, pretty close to the axle. Somehow they were rubbing inside the tube and over 14 years wore through to the copper. Every time I replace a fuse it would work fine in the driveway but by the time I got to the lake, the fuse was blown. One of the lakes is only 5 miles away.

You can check the terminal connections but your best bet may be to pull the harness and check the whole thing for bare spots.

 

[Dodger1234]

Thanks bassman284. Yep, I am going to pull the whole harness.

Dodger1234

 

[smokeonthewater]

I suggest that instead of checking it you simply replace it...

Wire insulation doesn't last forever.

 

[alldodge]

My WAG would be pull the bulbs from their trailer sockets and see if there is enough rust in there to cause a trace to ground, thereby causing a blown fuse

 

[smokeonthewater]

And then toss them in the trash along with housings so you can replace them with led's lol

Assuming they aren't already led's

 

[bruceb58]

Yes...Sealed LED lights are the only way to go these days.