Trailer lighting issue

OK....Here is my story, and I appreciate any advice in advance.

The left side of my trailer lights were not working. (1) I checked the ground on the light, scuffed up the connection, and did the same with the ground at the ball. Nothing. (2) I took a volt meter to the plugin the goes directly to my light. I got a reading of about 10.5 or so. (3) I took the light and switched it over to the right side, where everything is working fine, and the light worked. Everything I read said 99% of trailer issues is a bad ground. The only grounds there are, are the grounds at the lights and at the ball correct? I have been so stumped that I (4) ran a whole new trailer wiring kit, and the ground at the ball used to be wedged between an old rusty bolt, so I inserted a self tapping screw right into the trailer this time. After the whole new trailer wiring, I put the keys in the car, and BAM, the same exact result. I am completely stumped. :dono

Take a test light and connect clip to 'hot side'. Then take probe end and find a good ground. On battery it would be hooking to + side and probe end on - side. <*)}}}><

On truck?

There should be a white wire in the group, that is the ground. Most likely it's grounded to a screw or bolt near the front where the wires come out of the tongue.

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Originally Posted by Coy

On truck?

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On boat trailer at light. <*)}}}><

If it's a late model truck, find the fuses for the trailer lights. Should have a separate fuse for each side. Get your book or google your truck. Some of them are pretty hidden and may not be in your regular fuse panel.

Since you have power and ground on right side,, I feel you are still looking at a bad ground at left light. They share same power, brown wire. <*)}}}><

Don't depend on the ball for ground. Make sure white wire is grounded on the truck as well.

All grounds havr been checked and re-checked. Agree some reading last night, I think Cray is on to something. Going to check fuse tonight. Thanks

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Originally Posted by Coy

All grounds havr been checked and re-checked. Agree some reading last night, I think Cray is on to something. Going to check fuse tonight. Thanks

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Is it the running lights/tail lights that aren't working or the brake/turn?

That same thing happened to me.....I worked for three days on it. I had checked the fuses in the fuse panel inside the truck and all were good. Turned out there is another fuse panel under the hood...big black box that says main load center or something like that. Took top off of it and there were individual fuses for each light left and right includeing trailer lights.....I looked and found a bad fuse there for the side of the trailer that I had been working on. I replaced that fuse and all was good again.

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Originally Posted by "G"

That same thing happened to me.....I worked for three days on it. I had checked the fuses in the fuse panel inside the truck and all were good. Turned out there is another fuse panel under the hood...big black box that says main load center or something like that. Took top off of it and there were individual fuses for each light left and right includeing trailer lights.....I looked and found a bad fuse there for the side of the trailer that I had been working on. I replaced that fuse and all was good again.

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I did this exact thing. Ford 150 fuse was under the hood in fuse box.

Mine was on a Chevy Z-71

Thanks G. I am thinking that is the issue. I went out last night with my volt meter and tested the Brake/right turn/and left turn pins from my 4 pin plug coming out of my truck. All had power except my left signal. I looked through my owners manual, and there is a fuse that is responsible for my left turn/brake tow trailer. FYI 2006 Ford f-150. Wanted to post stuff like this in case this happens to someone else. Will check the fuse tonight and post on here the result. Thanks again for all the responses.

Sorry, my mistake.:Doh: I thought we were dealing with a running light, not a brake/turn signal light. <*)}}}><

As a retired electronic tech. When troubleshooting any electrical problem always look for easiest fix first. When you determined bulb was good. Your very next step should have been to read power at towing plug. This way you isolate problem to truck or trailer itself.

Not being critical here just trying to save someone else needless expense. Early in my career I was teamed with a crusty old codger that was a troubleshooting ace. He claimed he was the laziest person I would ever work with. That is why he honed his T/S skills to perfection. His credo was " necessity was not the mother of invention but just laziness. "

Over the years I came to appreciate his talent. Into taking a seemingly complex problem and breaking it down to a pure logical pursuit. His technique served me very well whenever I had to T/S anything. His one other saying was dead on too. " Regardless of the cost of your toolbox. The best tool you have is between your ears. Learn to use it first. "

Issue solved! It was the fuse the whole time. My truck has a fuse responsible for my left side tow blinkers and brake light. It was blown. Even though the brown wire was spliced and the right side worked, my left side brake wouldn't light with the blown fuse.

Great. If fuse would happen to blow again though. It may reveal a fault ( intermittent short ) in trucks wiring. Its not uncommon for a fuse to fail .

But if it continues to blow fuses then it has to be dealt with.