Okay I have been thinking about the 2 trucks I have had to rewire thier back halfs from fires in the wiring harness. Both were towrigs and both were towing when it happened. I think it was caused by a back feed from the batteries on the trailer into the truck. There is not protection from the trailers 2 batteries and the vehicle wiring harness as when the trailer plug is connected it is a direct connection.

I am just curious what people are doing to prevent there tow rig from having the same problem? Is there diode's that are large enough to take the 20amp charge and not backfeed that I don't know about?

I am putting dual batterys on my trailer for the winch and there will be a load centre on them but as of right now nothing to protect the truck?

I never really thought about this and I am all about always using fuses at the battery lol. We've all seen car fires started because someone installed an alarm, stereo, lights or other accessory at the battery without installing proper fuses to prevent short circuit electrical fires. Well the best solution is to simply fuse or run a circuit breaker at the trailer battery. I'm actually seeing a need for a fuse at the trailer breakaway battery also which is almost never fused-a self resetting cirucit breaker is the proper way to fuse an electirc brake circuit but I almost always uses a 30 amp fuse lol. I would not recomend a diode as there is a loss of like .8 volts across it so your charging times will go up and that along with voltage loss over the long distance may result in a battery never really topping off with a full charge unless you drive a few days if the batteries get low lol. Yep just uses a 60 amp fuse if your running 10 guage charging wire and you should be good. Check the fuse after you start your tow rig to be sure your trailer batteries are not backfeeding the towrig when you hit the starter but with a 60 amp fuse I can't imagine it blowing unless the tow rig batteries go dead or low. If this is a problem you can use relays to creatively isolate the charging lead when you hit the starter. Hope this helps...I think I have some wiring issues to address on all my trailers lol!

Jason :)

My 10 GA charge lead comes from a constant duty solenoid under the hood through a 30 amp circuit breaker to the trailer battery. The trailer battery is only in the circuit when the truck is running. I think 60 amp is too big for 10 GA wire.

Additionally, the factory truck's tail light wiring only runs the coils on some bosch-style relays which I have mounted under the truck. The relays are doing the work of lighting the trailer lights. The power to the switched part of the relay is also coming from an additional 30A protected 10 GA wire to the truck. So for the cost of about $20 worth of relays and sockets and a few $5 breakers there is basically no way I can hurt the truck's wiring with a trailer - even if every wire on the trailer is tied in to a big short.

A third 10GA wire protected by a third 30A breaker goes through the brake controller on the way back to the trailer brake pin.

I have to tow a lot of rental equipment trailers and some of the wiring on them is so screwed up, that is why I did it that way.

I guess I could add in a relay that the coil is fed from the 20 amp circuit breaker from the truck. This way the relay only allows a connection to the truck when the truck is connected and nothing without.

I plan to have a winch and a couple of lights on the trailer as well as a voltmeter to monitor battery levels. I also have a 5W plusetec charger to keep the batteries on the trailer fresh.

All my mods on my truck are isolated from the OEM harness via an auxillary panel off the battery with a resetable circuit breaker.

The trailer harness for F250/F350 is fused separately so any backfeed would stop at the fuse.

I ordered some relays for trailer wiring on my '90 D350 the other day, but they haven't gotten here yet. I'd really like a separate little fuse panel thing for it all... what's a good one to buy?

I am a huge fan of the bluesea panels personnally.

http://bluesea.com/category/5/21/productline/126

http://bluesea.com/files/images/product_lines/126.png

That looks great... will a circuit breaker "fuse" fit with the cover on?