Fuse problems on turn signal circuit

[markrinker]

Truck #2 has started blowing fuses on the turn signal circuit. Has always happened with trailer in tow, so focused on finding a short on the trailer to no avail. Never blows right away, like a dead short would.

Swapped out flasher unit, thought I had it licked. Soon no turn signals again. Had been running a 20-amp fuse, now bumped to 30 and its held for a few short trips. We'll see what today brings.

Any ideas? Is it normal to increase the fuse rating when running a trailer? Never had problems before...

[MTTwister]

Mark - you haven't had any mice moving in, have you? Couple of those little buggers chewed up some of the wiring on the horse trailer couple of years ago, and naturally where it could all ground out (but at least I could get to it to fix it. might want to crawl under and look around.

[HowieE]

In general it is not a good idea to upsize the fuse when adding a trailer. The fuse was sized for the original wire size and Lord knows GM did not build in any extra. If your trailer has a number of lights a better idea is to run a 12 volt supply to the rear of the truck, most GM have a battery wire already back there, and use that to feed power to relays on each circuit in the trailer. If you use the GM wire fuse it for 30 amps at the battery end and fuse each of the relay outputs for 20 amps. Doing this on the parking light circuit will removes any load from the parking light protion of the headlight switch, a very week point in GM trucks. Doing it on the signal lights will remove the load from the flasher circuit.
If the problem is only while towing I would take a 12 volt battery and rune the individual trailer circuits with a 10 amp fuse and seeif any blows the fuse.
Find the ground terminal on your trailer plug and attach the ground side of the battery to it. Put a 10 amp fuse inline with a jumper from the positive side of the battery and touch each terminal on the trailer plug. Have someone stand behind the trailer and watch the lights as you cycle the lights. If you have a dead short in one of the circuits it should blow the fuse. If this dose not produce results leave the battery attached to one circuit and try and wiggle the trailer wiring harness in as many places as you can to see if that produces a short. Do this for each terminal on the plug till you find the short.

[TAG]

have seen several automatic eq. trucks do this. was shift interlock solenoid more times than not.

[markrinker]

Thanks for the ideas. I'll try them and report the results. For now, a 30-amp fuse got me through the day. I don't think its a dead short, or even intermittant one. Something is simply drawing LOTS more juice than before.