trailer/running light fuse question

[Shizzy]

when I went to hook up my boat to my 03 Ford Ranger I found the Running lights didnt work. All other lights worked fine. Factory harness on the truck and all new wiring and lights on the trailer. A simple RTFOM and I found the "trailer/tow" fuse was blown. I replaced it and have had no further issues.

My question is what is the reason Ford would only run the fuse for the running lights and not all of the lights that plug in to the trailer harness? Also since the truck has a factory towing harness Im assuming the blown fuse was due to a trailer the previous owner pulled with a short?

 

[jtexas]

Re: trailer/running light fuse question

My ford has a trailer taillight fuse, a left trailer turn/brake fuse, and a right trailer turn/brake fuse.

apparently the turn/brakes pull a lot of amps.

sometimes a fuse blows for no apparent reason. you get voltage spikes in automotive DC wiring sometimes, whenever a motor turns on or off, or relays going on & off, some stray current.....sometimes it's a mystery.

 

[Shizzy]

Re: trailer/running light fuse question

that makes a whole lot of sense. I didnt look far enough in to the Owners manual.

 

[Rogue427]

Re: trailer/running light fuse question

I have a 05 F350 that pops that same fuse and my friends 03 F250 does to.

 

[Silvertip]

Re: trailer/running light fuse question

The reason the running light fuses blow is that any trailer over 80 inches wide has nine extra bulbs on that circuit. If each one took 500 to 700 mA that over 6 more amps on that circuit in addition to what the tow vehicle already has.

 

[jtexas]

Re: trailer/running light fuse question

in that case, an LED light kit oughtta just about solve the problem

 

[Silvertip]

Re: trailer/running light fuse question

Or install a $5.00 relay and send a separate +12 volt line to the relay. Trigger the relay from the tail light circuit and have the output of the relay feed the trailer running lights.