Trailer Blows Trucks Fuses - What?

[4winnsskipper]

Ok i have a 2005 f150. I've been towing my four winns on a shoreland'r trailer for years but was using the 7pin to 4 plat converter harness. I just now recently purchased a different boat and since the 4 flat harness was long i just plugged it directly to the truck's 4 flat. (the truck has tow package so it has both 7 pin and 4 flat on it)

So the lights worked just fined, towed the boat home 30 minutes at night, and as im making the last turn on to my street the running lights go out. So i assume the lights came unplugged. The brake lights and turn signals still work. So im sure i blew a fuse. I go to unplug then replug the light connector and the 4 flat harness on the trailer side feeels real warm which is ODD. I unplug harness then go to plug it back in and as the connection is made there's sparks!!! It seems there is a lot of current going through these tiny wires!!!

Where do i start? I definately blew a fuse and/or relay in truck, but something is wrong. Does this sound like it's on the trailer side? Is this just a bad ground on trailer or frayed wires? Just looking for a starting point or advice to keep me from completely re-wiring this trailer, which looks to be a PITA as there are lights near tongue, two on fenders, and two in back (naturally) with a 3 lighted bar in middle.

 

[MTboatguy]

Re: Trailer Blows Trucks Fuses - What?

Your running light circuit is shorted out somewhere, you have a bare wire touching metal, check the trailer first, I would assume it would be on the trailer..this is actually a pretty common problem with trailers..also make sure the trailer plug is not cracked, I have had 4 wire plugs break inside the plastic and create a short.

 

[12vMan]

Re: Trailer Blows Trucks Fuses - What?

Your running light circuit is shorted out somewhere, you have a bare wire touching metal, check the trailer first, I would assume it would be on the trailer..this is actually a pretty common problem with trailers..also make sure the trailer plug is not cracked, I have had 4 wire plugs break inside the plastic and create a short.

I agree with this.
Your biggest clue was that the plug was warm, which means there's a short and it's most likely on the trailer. I would start looking where the wires go in and out of the frame. Since it happened when you turned, the short is probably close to the tongue section. Sometimes the insulators that protect the wires get worn or dry out, crack and disappear leaving the plastic wire insulation prone to wearing through, letting the wire contact with the trailer.
Your running light wire should be the brown one.
I'll bet once you dive into this, you'll find the short within 10 minutes.

 

[jayhanig]

Re: Trailer Blows Trucks Fuses - What?

The brake lights and turn signals still work. So im sure i blew a fuse. I go to unplug then replug the light connector and the 4 flat harness on the trailer side feeels real warm which is ODD. I unplug harness then go to plug it back in and as the connection is made there's sparks!!! It seems there is a lot of current going through these tiny wires!!!

Where do i start? I definately blew a fuse and/or relay in truck, but something is wrong. Does this sound like it's on the trailer side? Is this just a bad ground on trailer or frayed wires? Just looking for a starting point or advice to keep me from completely re-wiring this trailer, which looks to be a PITA as there are lights near tongue, two on fenders, and two in back (naturally) with a 3 lighted bar in middle.

I think your problem is in the trailer wiring. If the short were on the truck side, the wiring on the trailer wouldn't be hot as the current would seek the easiest path to ground... leaving the downstream wiring still relatively cool. So rewire it and be done with the problem.

I recently acquired a used trailer that had its wiring patched together: the wire from the right hand taillight changed colors three times between where it exited from the taillight and where it terminated in the 4 prong plug.

All righty then. I decided the most effective thing to do would be to rewire the trailer and do it right. I went to Lowes and bought a trailer rewiring harness. For some strange reason it included a ground wire, a wire for the right turn signal, a wire for the left turn signal and one for the right side taillight. Nothing for the left taillight.

But that isn't too tough to correct. Both taillights need to be hot at the same time so it was just a matter of running a new wire from the right taillight up to the front of the trailer and then splicing it into the left's wire. I chose the front of the trailer to make the connection rather than just running across the back of the trailer because I thought it was better protected from the elements that way.

All connections were soldered and I applied shrinkwrap to the connections to make them watertight. In the back where I tied into the tail/turnlights I had to sand the wire strands a little so they'd solder acceptably. No big deal.

Everything worked fine the very first time I hooked up. Now to add on the goodies: I have lighted LEDs on the tops of the PVC guide posts I recently added. I ran their included wires up to as far forward as I could reach on the trailer, then attached them with the included splicing fittings. They are definitely NOT waterproof but they seem to work OK regardless. If they fail in the future, I will cut the wires and do the solder/heatshrink thing with them as well.

Now on my trailer, the turn signals have yellow and green wires; the taillight had a black or brown wire; and the ground wire was white (yeah, I thought that was strange but I didn't pick them). The extra taillight wire that I added was also either black or brown. So any additional lights that need to be added should tap into either the black or brown wires. They then either ground directly to the trailer frame or you just drill a hole and add a self tapping sheet metal screw and mount the ground that way.

There is a lot of satisfaction in having done it myself and I have a high level of confidence in the work I did. That trailer is in much better condition at this point than when I got it. (New rollers, new guides, new wires, new rims and tires.)

One last improvement: I have a backup camera in my truck that displays on a double DIN radio/DVD player in the dash. Backing up to the trailer hasn't been as easy as I hoped because it's difficult to make out detail due to the limited resolution of the camera. I added a little reflective tape to the very tip of the coupler on the trailer tongue. Now it lights up like a Christmas tree when I go into reverse and is very easy to couple up with the first attempt.

 

[Joshua Nichols]

Re: Trailer Blows Trucks Fuses - What?

Just re wire it.Like said previous. I use to work on trailers for a living and found I could save my customer money just by running new wire rather than troubleshoot the system.It's real easy and takes no time.... If you must really look for shorts.. This is where to look.. Where the wire runs around by the tongue.. Mid way around the axle( they get pinched back there) and at each taillight( sometimes some bozo replaces the whole light unit on either side and pinches the wire) If it has running lights, check those (same bozo put those on)Where the wires enter any tubes it there are any..You pulling it made the wire rub somewhere.. But willing to bet a dollar it's in the trailer not the truck..

Good Luck

 

[Baysidejoe]

Re: Trailer Blows Trucks Fuses - What?

Agree with all above. Most four wire harness have this color lay out: (white/ground) (brown or black/tail and marker lights) (green/right turn) (yellow/Left turn) the green and yellow also serve as stop lights..

 

[dmoriarty51]

Re: Trailer Blows Trucks Fuses - What?

not to hijack, but i have amber lights on my fender/step these need to be on the running lights correct? not turn signal

 

[jayhanig]

Re: Trailer Blows Trucks Fuses - What?

not to hijack, but i have amber lights on my fender/step these need to be on the running lights correct? not turn signal

Yes. Tie them in with the brown or black wire.

 

[Gary H NC]

Re: Trailer Blows Trucks Fuses - What?

Same exact thing happened to me the last outing.
One of my tie down straps on the rear of the trailer pinched the brown running light wire.
It was kicking the relay off under the hood.
It was just a small nick in the wire touching the frame.

 

[spdracr39]

Re: Trailer Blows Trucks Fuses - What?

The hottest spot is where the short is. My money is on a bad 4 blade plug either on the truck or the trailer.

 

[bruceb58]

Re: Trailer Blows Trucks Fuses - What?

The hottest spot is where the short is. My money is on a bad 4 blade plug either on the truck or the trailer.

Not a chance. Almost impossible for it to short there.

Its hot because there is a ton of current flowing through it!

 

[Fed]

Re: Trailer Blows Trucks Fuses - What?

The heat will be caused by a high resistance connection either where the wires go into the plugs or where the plugs mate.
A short circuit causing enough current flow to heat the plug would pop the fuse in a heartbeat, long before the plug actually got hot.

 

[bruceb58]

Re: Trailer Blows Trucks Fuses - What?

The heat will be caused by a high resistance connection either where the wires go into the plugs or where the plugs mate.
A short circuit causing enough current flow to heat the plug would pop the fuse in a heartbeat, long before the plug actually got hot.

You don't think 15 or 20 amps flowing through the plug may make it slightly hot? Depends on how long that amount of current is flowing through it. If it isn't quite a dead short, could be happeneing for awhile.

 

[Fed]

Re: Trailer Blows Trucks Fuses - What?

No Bruce, it will be a HR connection.

 

[bruceb58]

Re: Trailer Blows Trucks Fuses - What?

No Bruce, it will be a HR connection.

Actually, heat is caused by the power dissipated at a resistive connection. If the plug had a High Resistance, the fuse would not have blown at all becuase it would have limited the current. If the OP's case something as small as a 1/4 ohm resistance at the plug would have caused it to get pretty darn warm if 15A was flowing through it.

 

[Fed]

Re: Trailer Blows Trucks Fuses - What?

So im sure i blew a fuse. I go to unplug then replug the light connector and the 4 flat harness on the trailer side feeels real warm which is ODD. I unplug harness then go to plug it back in and as the connection is made there's sparks!!!

He didn't have a blown fuse.

I'm not quite sure what you're saying Bruce are you doing a backflip?

 

[4winnsskipper]

Re: Trailer Blows Trucks Fuses - What?

update: after going through all visible wires, pulling wires out where the wires run into the frame through rubber grommets (all in great shape) i found there was a ground wire running from a side marker to the common ground on trailer that was stuck between two pieces of the frame and frayed. This wire was a white wire though, not a brown (hot).... i tried to pull the wire out where it was pinched but it just broke and thats when i realized the copper inside was BLACK, as in it was burnt, i stripped the insulation back and the wire was still black so this is the only evidence of an issue i found after checking all light connections...could this be the culprit? im not sure because it was a frayed ground and not a frayed hot...no other lines i cut,stripped and checked that went from the 4 flat plug to both sides of trailer were burnt, just this one ground from the side marker. the brown(hot) wires going to this side marker were in fine condition.

btw since this is a shoreland'r trailer (1999 year) it's in great shape and all other wires look ok, re-wiring this thing will be a PITA!!! theres a total of three side markers on this thing, the taillights (of course) and the three bar light in the middle... and all wires run in the frame and have junctions existing inside the frame... so im gonna put a new 4 flat plug on, fix the common ground wire i found and see what happens....

oh and find out why i have zero power now at the trailer harness on the truck side, im guessing i blew a fuse or relay... suggestions where to look on my '05 f150?

 

[Joshua Nichols]

Re: Trailer Blows Trucks Fuses - What?

Normally those lights ground to the trailer frame at where they bolt on.. Some I guess run a ground wire too.. That blacked copper is not a good thing.. If you don't rewire now you will later sounds like to me.. You are the one to make that decision. Why is it a PITA? Cause it runs though those tubes? Use the old wire to pull the new stuff though.. If you could take the boat off.. It would be super easy.. Sounds like you are on the right track anyhow... Good luck

No more Four Winns?? Darn

 

[burp]

Re: Trailer Blows Trucks Fuses - What?

update: oh and find out why i have zero power now at the trailer harness on the truck side, im guessing i blew a fuse or relay... suggestions where to look on my '05 f150?

Ford truck's and SUV's have a fuse which powers ONLY the trailer marker lights. The 20 amp rated fuse is located in the fuse box under the hood (engine compartment), directly in front of the driver.

 

[bruceb58]

Re: Trailer Blows Trucks Fuses - What?

He didn't have a blown fuse.

I'm not quite sure what you're saying Bruce are you doing a backflip?

Where do i start? I definately blew a fuse and/or relay in truck, but something is wrong.

Sounds like he blew a fuse to me.

What I am saying is that the plug can get hot and it isn't the plug that is causing the problem. Replacing the plug is a waste of time.

For the OP, if you want to isolate it down to one side of the trailer or the other, you could cut one of the brown wires going down one side of the trailer to isolate one side.