electrical issues

[w6bauer]

Hooked up my trailer tonight to go pick up a truck and I ran into some issues. All lights on trailer and my truck work when the headlight switch is in off position. When I switch to running lighs or headlights everything works except brake lights on trailer, all trailer lights go dark when brakes are depressed. I checked and cleaned ground on truck and inspected connectors for corrosion and found none. All fuses are good. A few weeks back, just after using trailer I lost tail lights on my truck and replaced fuse which kept blowing when I toggled dimmer knob for dash lights all the way off then back on. Replaced headlight switch and fuse stopped blowing. Now I've got this problem of no brake lights when running lamps and headlights are on. Anyone run into anything like this or have an idea what it is?

Another thing I noticed when testing for current at the contacts for trailer harness I had ground wire of tester clamped to ground for taillights etc and I dropped positive lead for tester on the ground in some water and noticed I was getting voltage from vehicle ground to the pavement. Normal? I'm lost on this one please help

[DennisG01]

I'm not the best when it comes to diagnosing electrical stuff, but...

-- Are these problems only happening when a trailer is hooked up? Do all of your truck's lights work correctly when no trailer is attached?

-- Are the grounds on the trailer good? Or, is the trailer only grounded through the ball?

-- Do you get 12v at the appropriate pins on the truck-side of the trailer connection? Meaning, when you press the brake do you get 12v at the brake pin? etc...

-- What happens if you hook up a different trailer?

'Ya got me on the "positive lead in the puddle" issue!

[DickWells]

Are you using a digital VOM? I would think an analog meter wouldn't move up, if you dropped the pos. lead in water, but a digital would show a - minus voltage. I wouldn't expect to see any voltage, if the trailer lights weren't turned on, though, and only negative voltage at that, thinking that you're getting feed through a bulb fillament for ground, and the leads are reversed, anyway. But, I'm no electrician, so I'm just going by what's happened to me, on more than one occasion. And a full 12 V is confusing, because I don't see how that could be, given how much drag there'd have to be, through bulbs, wire, leads, etc.:confused: Dennis' info is right on, with what I've ever experienced.