Trailer Wiring Problem

OK, need some help here, last night I was on my way home from the river. As I was driving down the road I noticed my clearance lights on the boat trailer started to dim. I kind of figured it was a possible ground problem and when I got home I would be able to check it out. About 1 mile from home, my clearance lights were not working at all, hit a bump and they would come back on but again they were very dim. Got to the house and put the Jeep in reverse when I noticed a lot of smoke coming from the rear end. I jumped out and found the smoke coming from the driver side rear corner of the Jeep where the trailer wiring converter was mounted. I just replace the converter about 1 month ago and have had no problems, well last night the converter was on fire, I know what fire looks like because I’m a firefighter Thinking quickly I unplugged everything including the harness out of the converter. I backed the boat into the driveway and quickly disconnected from the vehicle and started to tear apart the cargo comparment to get the converter disconnected from the vehicle. So, my question is, is there a short in the trailer wiring? I know the converters are supposed to protect the vehicle from a short circuit, but I didn’t think that they were supposed to catch on fire. Do you think that I should just rewire the whole trailer? Any help would be appreciated. Thanks, Brent

I know nothing about converters…

But the first thing I would do is find out if there is a problem with your trailer lights or the truck…there could have been an issue with the converter.

Glad you didn’t have a major fire…that wouldn’t have been a good fishing trip.

My experience with wiring problems in general is to deal with them as follows: first, check to be sure that the insulation has not worn away somewhere on the wiring, which can cause problems. If the wiring is intact, re-do the ground to get a better connection. If that doesn’t work, rip out the wiring from which ever part of the rig, trailer or vehicle, is causing problems, and start from scratch with new wiring. I’ve spent time messing around with wiring problems in the past, and it usually came to this last step, anyway.

Being that fire is involved, you might want to check a little closer in to what the problem is, though. If there is a bigger problem than a short due to a poor ground or old wiring, the next fire could toast your entire boat and trailer before you notice it.

I’d want to know why the fuses didn’t blow. That’s what they’re there for, to protect you and your vehicle in case of a short. BrianK may be right in that the converter itself failed.

I’d measure the current it takes to light up the different bulbs on the trailer. I’d use a VOM and a battery. Assuming there aren’t any shorts in the trailer wiring, then I’d look at the vehicle and make sure the correct sized fuses were in place for the rear lights.

Rootski

It could have been the converter, however, I have never experienced, or heard of any problems with them. A short can cause the problem, but I dont see how it could be a direct short because that would blow a fuse immediately.

My guess is there is a poor connection that caused the problem.. rather than steady power going through the wires.. it was repeated power surges that built up heat, eventually ruined the insulation, and eventually started the fire when there was never enough of a *short* to blow the fuse.

It is not impossible it was inside of the converter(booster on a jeep). Jeep trucks have very small wiring that they tie into and I would guess the source was right there.. its really hard to tie into a 20 guage wire with a little *dummy clip*.. a wire that small is prone to breaking. I suppose its still possible it was a bad converter and eventually built enough heat to ignite.

Brian made a good point.. The 1st thing you want to do is be positive you have no problems with the trailer wiring. I would go as far as to remove all the wiring and inspect every inch of insulation on every wire.. exposed or buried. Replace it with new… why tempt fate? If you really want to go the extra mile you can switch over to LED trailer lights and side markers which draw only a fraction of the power, and at the same time would greatly reduce the chance for a short at a later date with less current draw.. less draw, less spark.. not to mention no more burnt out tail lights!

Good luck.. I would really spend the extra time to find the source.. my guess is you will be yelling at someone. Either the company that installed the converter, or the company that made it.

For it to light-up like that it had to be a dead short to ground. The fuses are there to protect from regular surges and pinched wires. Fuses should blow if it is on your trailer. Our guess is that someting is awry in the vehicle. Even 12 volts can melt a cresent wrench if the circuit has a short to ground.

Good Luck!!

Dan and Tim at Trail’s End

Hey! Welcome Trailsend!

It’s going to be nice to have some Pro’s on line!

I forgot to mention that this is the second coverter on my 99 Grand Cherokee. I thought that converters were designed to get there power straight from the battery so incase of a short it wouldn’t damage the vehicle wiring, which you could say that it did if you look past the small fire. The first converter failed when I was hauling the boat to put away for storage, and I picked a bad day because it was snowing. I thought that maybe something in the trailer shorted out or maybe there was a bad ground. This spring when I finally checked it out, I found the converter wasn’t working, so I replaced it. I haved towed a camper with it for years and never had a problem, also towed my old boat with no problems. My current boat I have had for over a year with no problems until now.

I’m not sure what you mean by ‘converter’ but am assuming that it is the trailer plug on the vehicle side. If that is the case, is this a hard-mounted plug recepticle, or a pendant 4-wire connector that swings underneath the bumper during regular driving?

My guess is that due to normal twisting, bending, and turning of the wire, there is internal breakage in the copper. Stranded wire is used, and if enough of them break, leaving only a few remaining to carry juice to supply the whole trailer, then those remaining, unbroken wires are carrying in excess of their capacity.

Let’s say, for instance, that standard automotive DC supply wire was used (10 gauge stranded, 105C insulation rating). The carrying capacity of the wire is something just over 30 amps, so in a normal case, a 20 or 25 amp taillight fuse would blow before you ever had any heating problems with the wire.

But…

The wire itself is actually a bundle of 36 guage wires, which, hanging below your bumper are constantly swaying under the influence of airflow beneath your vehicle. When your trailer is connected, it is pushed side-to-side with every turn or bend in the road, etc. The individual 36 gauge strands are about 5 mils in diameter, and are actually quite prone to breakage. Safe current carrying capacity for a single 36 guage wire is something on the order of 0.03 amps, so you’d better believe that it’ll burn before anything blows in your breaker box. Intermittent contact between the remainig threads can also cause excessive heating and start to burn the insulation.

Of course, after all that, it could just be that a mouse has built a nest up in there and started chewing on the wiring, too.

Let us know what you find out, I’d be interested to see what final resolution of this turns out to be.

Most trailers operate on a four wire system where the brake lights and turn signals operate on the same wire. When the towing vehicle has separate wires for brake lights and turn signals, a device called a taillight convertor is required. – look at a Jeep Grand Cherokee – brake lights are red, turn signals are amber – therefore converter is needed.

The 4-flat connector on my vehicle used to dangle when not is use, but when I installed the new taillight converter, I took a 7-way round and took out the insides, so my 4-flat could stay inside of it out of the elements, it doesn’t swing around anymore what so ever, and I really don’t think that I picked up a mouse in my vehicle, and the problem started before I put my boat in storage, so I don’t think that a mouse caused that problem either.

a convertor, simply has an extra wire, (RED) to hook up to the stop lights. Right turn (GREEN) Left turn (YELLOW), Tailights (BROWN) Stop lights (RED) Ground wire (WHITE).

big g

You can check your trailer real easy with a battery charger as a 12V source. Hook up the ground clip to the trailer and put a nail or screw in the positive clip. You can touch each of the leads on the trailer and check out if it is OK. Brown is tailight and and yellow and green for the signals and brake. If that is all working I think you know the answer is the convertor. I had the same problem on my old van. Went thru about 4 convertors in 6-7 yrs. I think most of them are just made cheap.