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John M

Trailer brake light intermittant failure

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John M

The right brake light on my SMP trailer is working intermittently but mostly not at all. The same light works correctly for the right turn signal and when the headlights are on. (There must be two lamps) All other trailer brake light are working properly.

I have a 2004 Suburban. The electrial adapter and trailer wire harness are tight. The right brake light worked fine two weekends ago.

I would appreciate any suggestions about what I should look at.

Thanks.

John

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Jimmy Buffett

Could be a couple of things. I'd start with the bulb itself and make sure it's tight in the socket. Also check the wire connection at the socket and make sure there's a good connection.

You can trace the problem if you have a multimeter. Start at the vehicle adapter and check the voltage there. Then connect up the trailer wire harness and check it at the light fixture. Visually inspect the wire to see if it is frayed or pinched anywhere.

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D-GOOSE

I have to agree with Jimmy. I would think that its in the trailer light area. Bad ground or buld. But def check the wiring and light socket.

How is the brightness of the right turn light. the turn and brake are the same eliment and wire. If the turn is working but dime I would lean more to a grounding or socket problem.

I don't think the chevy has two relays (one for brake and one for turn). But then I have been know to be wrong. If your not getting great power from the truck plug let me know I will look up your wireing diagram.

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Sunsetter95
I have to agree with Jimmy. I would think that its in the trailer light area. Bad ground or buld. But def check the wiring and light socket.

How is the brightness of the right turn light. the turn and brake are the same eliment and wire. If the turn is working but dim I would lean more to a grounding or socket problem.

I agree with them also.

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Chauncemaster

I'd use a little LED tester if you have one or a multimeter to make sure the vehicle is putting out the signal correctly before messing with the trailer.

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Faceplant409

It is probably where that light is grounded (sometimes the mounting screws or rivets are used as ground) to the trailer. Also if you have a swing away tongue sometimes they ground to the swinging part of the tongue. I ran a jumper from the swing to the "trailer" and fixed my problem on my old Sport Boats trailer.

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mikea

whenever i am working on trailer lights i make sure that i put the trailer on the hitch. it will help alot with grounding issues.

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Lakenut

Check you fuse box under the hood of your truck. I had what I thought was a bad brake light on my trailer last year. I replaced the light unit. No fix. Then I started testing wiring all the way up to the truck. No problems.

On GM trucks there is a seperate fuse for left and right trailer lights. I had a bad fuse.

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whiteVLX
On GM trucks there is a seperate fuse for left and right  trailer lights.  I had a bad fuse.

Well who'd a thunk that?

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SunriseH2OSkier

I'd use this as a great excuse to upgrade to LED taillamps. "Well honey, I hate to have to spend the money, but it is just too dangerous not being able to trust that those taillamps are going to work." Innocent.gif

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SmoothWaterMan

Ford is same way - running lights and brake/turn lights are different fuses.

Now, my guess on an 01 is that the bulb is a sealed unit. It's typically a single bulb. An easy way to check brake and turn signals is just put on the hazard lights. If both left and right flash, then they work fine.

Now, if you have a brake light, but no turn signal, you might make sure you have a signal coming from the tow vehicle first, as mentioned above. Then look for a bad ground or bad connection.

pb.

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Lakenut
Well who'd a thunk that?

No kidding. I was glad that it was that simple but frustrated that it took me aver an hour to come to that conclusion.

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D-GOOSE
The right brake light on my SMP trailer is working intermittently

It would not be a fuse.

Did you find out what it was???

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jvianco

I had that last year with my SMP trailer, and it turned out to be a bad ground on the wiring harness on the truck side.

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dlb

I had the same problem with my Suburban. Changed the fuse and everything worked for a while then......same issue but the fuse was fine. I checked the ground wire and it was loose. Fixed it again......then same issue.

I could have been the cause of the ground wire being loose due to my checking everything when it first happened.

This was all in a 3 week or so period.

Upgraded to rear LED's and haven't had a problem in over a year.

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andyb

The current required to run LED's is lower.

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malibanker

Check you fuse box under the hood of your truck. I had what I thought was a bad brake light on my trailer last year. I replaced the light unit. No fix. Then I started testing wiring all the way up to the truck. No problems.

On GM trucks there is a seperate fuse for left and right trailer lights. I had a bad fuse.

Ok, so this tip ALMOST saved my day. I spent hours trying to figure out why my running lights weren't coming on after replacing the left rear brake light and red running light. Brake lights and turning signals worked fine, my only issue has been getting the running lights to come on.

came home, found this thread, and sure enough I pulled open the fuse box under the hood and I had a blown fuse.. woo hoo! Since I was still monkeying with my new red running light I left it off and plugged in the boat... since it was 930pm (started project at 1130am) all the running lights lit up like a christmas tree... it was my Clark Griswold momment.

now here is why it ALMOST saved my night. I unplugged the trailer, dropped in my new red running light with new screws and all, plugged it back in and no lights! checked the fuse and it was blown again. brake lights and signals still worked, just not the running lights.

so what is causing my fuse to break?... given the amount of time I've spent on this project it should be obvious that I am very novice.

1. do i need a stronger fuse (has a 15 in it right now)

2. Do I have a bad ground some how? the little red light only has one black wire going into it. the assembly has a metal 'tag' about 1/2 inch long that goes from the point where I plug in the black wire and connects to the screw that holds the assembly to the trailer itself (these are the screws I replaced before I knew the fuse issue). I imagine this is the ground wire.

The black wire that attaches to the red running light is spliced into the red tail light and the license plate light. I See a ground wire (white) that comes from the tail light assembly and it is firmly attached to the frame.

Thanks in advance to anyone that can help! The good news is I'm only pulling the boat about 20 yards to our boat ramp tomorrow! I imagine its an easy fix but I just don't know what to look for. Before fixing the fuse, I cleaned the connections to the truck, re-spliced wires with and replaced the old caps with new ones.

2009 tahoe, 2005/6 Dorsey tandem trailer.

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Beau

Whenever I have any trailer light issues I always first start checking grounds. Over the years I've found that most of the time, any trailer light issues usually are the result of poor continuity to ground.

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wienrdog

You likely have a pinched or rubbed off wire somewhere in the trailer - it will be a bear to find.

It's likely in the running lights - since you didn't have the turn signals or brake lights.

You can start checking where the wires go into the trailer & anywhere there is a flexible tongue, etc. Could also be the new running light - make sure your connection to the black wire doesn't have any bare spots that could be contacting the trailer before going thru the light. You shouldn't need even a 15A fuse in there. My truck has a 3A fuse & it's been fine.

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