No power to running lights on trailer

[JoyfulDiscontent]

I'm stumped. Brake lights and turn signals work on trailer work fine. No running lights though. Bulbs are good. Wiring on trailer seems to be good. Used multmeter to check for continuity. As far as I can tell, fuse is good. I beleive this fuse is a 20A fuse in the distribution box (correct me if I'm wrong). I decided to take out the bulb and bypass all the trailer wiring just to make sure I've got power. Knowing the bulb is good I connected the running lights power (brown wire) to one bulb wire and grounded the other bulb wire. The bulb does not light up. I checked the relay and that is still working. I can hear it click so I assume power is reaching it. I'm not an electrical wizard so I don't know if testing the power this way should work. However it did work for the turn signals so I assume it should work for the running lights.

There is probably a better way to diagnose my problem and after spending the last two nights working on it I'm hoping to get some insight. Is there a sure fire way to determine whether the problem is with vehicle and not my trailer?

BTW - It's a boat trailer so the sooner I get it fixed the better. Minnesota summers are too short to miss out on good fishin'.

Thanks,
Aaron

 

[Gator Jeff]

I'm assuming 4 pin connector right? The brown wire should power the tails, brakes and running lights. Are the same brown wires that power your tails also powering your running lights?

 

[IZwack]

Is there a sure fire way to determine whether the problem is with vehicle and not my trailer?

Disconnect the trailer and test the pins on the connector on the vehicle -- turn the lights on and the running lights pin should go to high voltage. If no voltage, then the problem is on the vehicle. You already stated that you checked the fuse (using the multimeter I'm assuming) so the next step is to see whether or not that fuse is getting power so take the key out of the vehicle, pull the fuse, put the key back and turn on the lights. Then put the multimeter's probe on one of the fuse's receptacle's pin and ground against the body/chassis. If the voltage doesnt go high, check the other pin of the fuse's receptacle. If both pins are dead, then the problem is upstream of that fuse. If one of them goes high, then the trailer running light wire is broken somewhere after that fuse.

If all else fails, you can tap one of the rear brake lights' parking lights (hopefully the fuse will handle the extra load).

 

[aklmfreak]

i had the same problem with my 2000 sport, it took me forever to figure it out, i used a multimeter to check the plug adapter under my bumper and it was getting no power to the running light terminal. but i looked in my user manual and found which fuse was for "Trailer Tow Relay (Parking Lamps)" and sure enough it was blown. (the fuse is number 30 on my panel) it's a 15 amp fuse.

i suspect that the reason it blew was because it either shorted when i backed the trailer into the water, or because there are 8 running lights on my trailer, which may be pulling more than 15 amps, i dont know

but i hope that helps you out

 

[budwich]

what aklmfreat said... check that the relay is being pulled up... if not check the associated fuse.

 

[xchris]

I definitely have power to the left and right turn at the trailer pigtail. Just no power to the running lights at the pigtail. I never had an owner's manual for this truck. Can someone anyone tell me which fuse is for the trailer pigtail running lamp? It ain't #8 or #30 under the dash. Heck I'd be thrilled with a link to either the owners manual for this (2002 Explorer) truck or just a fuse box diagram.

Thanks