trailer running lights problem

[wil.hansen]

So... I've been having some trouble with the wiring of the trailer lights (completely separate from my trailer electrical system). I finally fixed a grounding problem and got the lights working for a second. Then, without disconnecting the tow vehicle, i was messing with a running light wire and saw a small spark, and now the running lights don't work. The turn signals/brake lights work, but NO running lights anywhere on the trailer (still work fine on the car). I'm thinking it is a blown fuse? only... where would I find that fuse? I'm so confused
..and tired of thinking about this problem.
thanks for the help.

[dh]

Check voltage at the trailer connector on the TV. A simple test light will do. If nothing, is your light connector factory? Many factory, or dealer installed trailer light systems utalize a relay(s) so the trailer is isolated from the vehicle's electrical system.
If its a factory job, look in the owners manual for the fuse loation. If its not a factory job, look under the hood for anything that doesn't look factory , look for fuse holders close to the battery, or underhood fuse box.

[dh]

If you still need more help, the more details you can provide the better.

[bobhenry]

Unplug the trailer, drag out the battery charger , ground the negative to the white wire ground or the trailer and clip the hot lead to a small screwdriver , with the screwdriver touch the brown pin in the trailer harness. What happens ? If it looks like you are arc welding you have a direct short. Look where you have dragged the wire thru metal, perhaps the insulation has been scraped leaving bare wire touching. There may be a chance you have inadvertently connected a ground wire into the positive lighting side. ( don't laugh I have done it and it will drive you crazy trying to find it ) On the grounding side the spark could have been the juice jumping to seek ground. Things don't work well when they have to work that hard to make connections. I have a piece of wire 10 - 15 feet long with two good sized clamps I can clamp it directly to the tow vehicle frame and go back to the offending light and ground it. If it comes on it just doesn't have a good ground. Hard wired grounds to any and all light fixtures is a time consuming PITA but it sure makes the running light headaches diminish. Let us know what you find.

P.S. If this happens to be a harbor freight trailer ground the actual lamp socket by installing a small worm clamp around the lamp socket and trap a wire with it and run it to a known ground. For some reason the lamp socket doesn't always have a ground. ( yep took some head scratchin to find that one )

[bobhenry]

So... I've been having some trouble with the wiring of the trailer lights (completely separate from my trailer electrical system). .

PSS. How in the world are your trailer lights seperate from your trailer electrical system ?

[Dale M.]

So... I've been having some trouble with the wiring of the trailer lights (completely separate from my trailer electrical system). .

PSS. How in the world are your trailer lights seperate from your trailer electrical system ?

What he is saying is convenience lighting in trailer is different system for towing light system powered by TV....

Also problem may be a lot of newer cars & trucks have completely different set of wires going to trailer connector with their own set of fuses and they are completely isolated for "TV" lighting system...

So in many cases the TV lamps function fine but the trailer is not functioning because of blown fuses or poor wiring in TRAILER portion of fuse box or harness.....

Chevy PU's ( just one such vehicle) have uses this 'isolated' system for years.... Chevy PU's have a complete set of trailer light fuses in fuse box next to battery.... Check owners manual to see if your TV has such a feature....

Dale

[wil.hansen]

ill do some more snooping today and let you know what i find.

I DO know that there is a fuse block next to the battery in the TV, additionally, one under the dash on the driver's side. So, maybe I can find that blown fuse - seems this would be my best case scenario.

I may post some pictures to help you get a better idea of what I'm looking at.
-w

[bobhenry]

So the running lights are isolated from the courtesy lighting system.

Sorry my bad ! I just read it funny I guess !!

So at this point can we assume you have tested for power at the plug on the tow vehicle and found none for the tail light circuit. ( generally brown wire on trailer) ???

[wil.hansen]

So, I looked through the manual and found the fuse associated with the running lights... too bad it is for the regular running lights and not 'towing' running lights. (plus, it wasn't blown anyway). I tested the flat 4 on my TV and got this:


after searching around, i found where they installed the connections for the towing (after market) in a little compartment in the back:



What really confuses me is that the rear lights are working fine with brakes and turn signals, but NOTHING when i turn the lights on - same with my amber running lights in the front of the trailer. It's hooked up according to pretty much ALL schematics ive seen. I'm just at a loss.

[wil.hansen]

Unplug the trailer, drag out the battery charger , ground the negative to the white wire ground or the trailer and clip the hot lead to a small screwdriver , with the screwdriver touch the brown pin in the trailer harness. What happens ? If it looks like you are arc welding you have a direct short. Look where you have dragged the wire thru metal, perhaps the insulation has been scraped leaving bare wire touching. There may be a chance you have inadvertently connected a ground wire into the positive lighting side. ( don't laugh I have done it and it will drive you crazy trying to find it ) On the grounding side the spark could have been the juice jumping to seek ground.

i have a battery tender.. which i guess i could use to test the flat4 on the trailer. so a electrical jump means there's a short somewhere? what if nothing happens? everything's a-okay?
this is taking up my whole day... such a bummer to lose time to fix problems like these... but I guess that's all part of the build, eh?

[parnold]

I had a similar problem with my running lights, and all testing I did with meters led me to believe it should all be working. It turned out to be a crappy connection behind the tail light, where the wires from the little box went. The meter would show voltage, but when the trailer was plugged in, the draw was too much, and the lights wouldn't light.

[wil.hansen]

so, i tested the trailer side connector with the battery tender. nothing happened, at all.

so... since the rear lights work with the signal/braking, i decided to isolate them. I connected the brown wires straight to them (bypassing the amber markers) signal/brakes still worked fine, but still no parking/running lights.
this makes me thing that it is NOT a grounding issue.

the small box ("regular duty circuit protector") makes me think there are fuses inside to protect the TV's electrical system. But it seems as though there is no way to get that box open.

My flat4 on my trailer has 2 brown wires coming out of the same little prong. I assumed that one runs down the left side and one runs down the right side. maybe one is a neutral wire and one is a hot wire? I don't know. I guess I'm leaving all options open right now.

[parnold]

Stick a safety pin in the wire going INTO the little black box that carries the 12v for the running lights. Turn everything on, plug in the trailer and see if you have 12v there. It sounds like you have the same exact problem I did. I wasted hours of time isolating each stupid marker light and ground.

[parnold]

Oh, the two brown wires are both hot, and typically, one goes left, one goes right, just like you speculated.

[wil.hansen]

so, just for fun.. i switched the connections on the brown wires with the green/yellow on either side - i figured that this would tell me if there was a short in the trailer wiring.

result: the brake/signals worked (with the different filament) but the running lights didn't; and since i still have the rear lights isolated, this tells me that there is no short in my wiring on the trailer side.

I guess that means that there is a short somewhere in that flat4 connection or in the circuit protector box.

sounds logical, right?