Latest Crisis!

Trailer has brakes but not a single light comes on. No running lights, no signal lights and oddly enough, even with brakes no brake lights. Ground rings good from the coupler. What am I missing? Can't even get a lamp light with a 12V battery to the coupler.

Start from the very begining due to lack of finding anything in the middle...then work through in progression. to the trouble spot.

Broken wire inside the wire covering, is there anywhere it gets stressed a lot?

Richard S. wrote:Broken wire inside the wire covering, is there anywhere it gets stressed a lot?

I would think the trailer coupler wire would be the big stress point. But it seems like the ground is good, especially with the brakes working well. I should be able to power up one light from the coupler, they couldn't all have broken wires. And the brake light and brakes are the same circuit. They should light.

coaledsweat wrote:

Richard S. wrote:Broken wire inside the wire covering, is there anywhere it gets stressed a lot?

I would think the trailer coupler wire would be the big stress point. But it seems like the ground is good, especially with the brakes working well. I should be able to power up one light from the coupler, they couldn't all have broken wires. And the brake light and brakes are the same circuit. They should light.

Don't know you trailer but most trailers brake lights use the same bulbs, circuits, as the turn signals. They are usually separate from electric brakes on a trailer because the lights are on or off and the brakes apply more as the brake is applied more in the tow vehicle.

pyma wrote:Don't know you trailer but most trailers brake lights use the same bulbs, circuits, as the turn signals. They are usually separate from electric brakes on a trailer because the lights are on or off and the brakes apply more as the brake is applied more in the tow vehicle.

There is no separate circuit for the brake lights, it is the same as the brakes. Granted it uses the turn signals, but no lights work. Turn signal, running lights and brake lights don't work.

There must be some controller on the trailer to separate, adjust voltage to the lights from the brakes otherwise the brakes would be on or off. Could be a problem there. But not for the running lights, there has to be a break in the circuit, wire.

Run a separate ground from the truck to the trailer to rule out ground. Jumper cables work well.

You could also run a test light from pos side of vehicle battery back to the trailer frame to check for Ground.

coaledsweat wrote:[quo

There is no separate circuit for the brake lights, it is the same as the brakes. Granted it uses the turn signals, but no lights work. Turn signal, running lights and brake lights don't work.

Don't know what system you have, but I have seen electric brakes get shorted to the turn signal, then every time the signal blinks the brakes come on HARD. If the brakes were wired directly to the brake light circuit the same thing would happen whenever the brake light came on. You're drifting up to an intersection, lightly apply the brakes and the trailer locks down tight. So there must be some separation between the two circuits.

Maybe describe your brake setup along with manufacturer and model numbers would help. Otherwise get out your DMM or test light to check the light plug on the truck. From there use an ohm meter to check continuity from trailer plug to light bulb. Then get back with your results.

Fuse?

Everything seems to ohm out correctly. Brakes work flawlessly on their own, have to see if they come on with turn signal. No lights, even with a 12V battery feeding the coupler.

Its a 20' Hudson Brothers lowboy. I'll try and attach the diagram, 7 pin semi style coupler.

When things are crazy it always is the ground. I cannot tell you how many symptoms I have seen that the ground made it happen, usually on my friends equipment because I am a ground nut on my stuff.

That's what I'm thinking. Ground rings on the ohm meter but the number is odd. Shows like 6 when everything else displays 3 digits. Must be that the brakes have a seperate ground from the lights.

If you look at page 72 it says brake wire/red and brown. To me that says it indeed has a separate ground. That would explain why they work but nothing else does. All lights are grounded to the frame.

Did you try a jumper cable between the truck and a ground on the trailer CS?

Just noticed on page 73 there is a junction in the junction box. It's pictured where the battery (-) ties in with the ground wire. One red/brown goes into the trailer plastic pipe, one is headed towards a ground lug.