Parking lights lock up trailer brakes! - Diesel Forum

Sabre2th · 12-25-2006, 08:36 PM

Hauled a load of hay for mother-in-law today (~100miles) parked my 24' gooseneck when I got there, hooked back up a few hours later and started down the road. Switched on the headlights (for safety of course..) and the brakes on both axles locked up. WTH? [img]/ubbthreads/images/graemlins/confused.gif[/img] Left the lights off on the way home and the brakes seemed to work OK. Where's the best place to start troubleshooting this problem? Truck or trailer? Ran the lights on the way there, no problem.
Thanks,
Tom

shitface · 12-25-2006, 09:14 PM

In theory, your lights should come on when you apply the trailer breaks then.

The trailer wireing should be exposed if it has an open channel frame, so start there. I'd look at both male & female plugs also, a stray strand of wire could be touching another post on the inside where the wire is screwed on. It could happen.

Are you SURE the brakes were working when you shut the lights off? Because the first thig I thought of was that you installed the plug at the wrong index. Yes, I know it has a groove to prevent that, but I have seen my parrents do it upside down and force it in, then drive 180 miles for me to see why nothing was working. DAH!

shitface · 12-25-2006, 09:21 PM

One more thing. CHECK THE GROUND! It should have a ground wire in each plug and both need to be attached to the frame.
I had a truck once that was doing all kinds of crazy stuff; license plate light was blinking when turn signal was on, all the lights seemed "connected" somehow. I was puzzeled. I took it to a shop and left it, the guy told me the bed was not grounded properly, so all he did was tighten the bolts that mount it to the frame. I had trouble later and added a wire from the frame to a fender brace on the bed and never had trouble again. Now the ground is the first thing I check when I have electrical gremlins.

PerryB · 12-25-2006, 11:43 PM

I second the un-grounded theory.

popups4rent · 12-26-2006, 10:32 AM

If it is not a ground, 2 chaffed wires are touching, I had this happen when the tail light wire got a hole rubbed through and contacted the brake wire that had also rubbed through.

Stroked & Stoked · 12-26-2006, 02:41 PM

I 3rd grounding as an issue. I had a trailer with weird lighting issues last year. Plug it into my buddies truck - worked fine. Plug it into mine all kinds weirdness. replaced my 7 pin recepticle and pig tail - still weirdness. Finally found a bad ground in the rear ramp door.

We came away with the conclusion that my buddies truck was simply providing a better ground from his chassis.

mjarx · 12-29-2006, 12:35 AM

Had a loose wire on one of the terminals in the plug once. Lights went out, fuses blew, Oh what fun on a dark night. The trip to the lake was uneventful, this all happened on the way home on the same day.

j_apetersen · 12-30-2006, 08:13 PM

Try checkiing your lights might have one shorting over to brake -turn and aplying the brakes threw the truck brake controller. but you should see the light on the controller come on. Do you have a brakeaway switch. if you do try disconecting it they go bad in the rain and fix themselfs after rain stops.