Trailer Brake Lights Stay On When Truck Lights Are On

[Harry6082]

My brake lights are lit continually when I have my truck and trailer lights on. How do I attack this issue? Thanks in advance!

 

[Rene T]

Welcome to forum.
Did they ever work right?
Had anyone worked on them before you found this issue
Disassemble the truck receptacle to verify all the wires are properly connected and not corroded.
Open up the junction box where the pigtail goes into. Check all the connections there

 

[Harry6082]

Rene T, thanks. Yes they did. I also have a horse trailer with a seven pin connector and the lights on the horse trailer work as expected. I will check the seven pin connector and the junction box. Thanks Harry

 

[John From Detroit]

My brake lights are lit continually when I have my truck and trailer lights on. How do I attack this issue? Thanks in advance!

The answer depends on the light type but often with traditional hot filament type lamps it's a ground problem Though ti's usually the tail's that light not the brake (higher wattage) element.

 

[Rene T]

Rene T, thanks. Yes they did. I also have a horse trailer with a seven pin connector and the lights on the horse trailer work as expected. I will check the seven pin connector and the junction box. Thanks Harry

My name is Rene and not Harry.

 

[Harry6082]

The answer depends on the light type but often with traditional hot filament type lamps it's a ground problem Though ti's usually the tail's that light not the brake (higher wattage) element.

John, thanks. It’s a 2008 Thor Summit so I guess the lights are of the hot filament type. I’m going to check the 7-pin connector and junction box per Rene’s suggestion and then work backwards from there. Harry

 

[Larry N.]

connector and the junction box. Thanks Harry

My name is Rene and not Harry.

It can be funny, and I often see it the same way, but a lot of folks forget that a comma or a "carriage return" can separate those two pieces for clarity.

 

[olly72]

My brake lights are lit continually when I have my truck and trailer lights on. How do I attack this issue? Thanks in advance!

This happened to my sons vehicle. It turned out to be a spacer between the brake pedal and pressure switch that turns the lights on and off. Look at the brake stem holding the brake pedal and you should see where the stem presses that switch. See if the spacer has worn down allowing the lights to stay on.

 

[Kirk]

My brake lights are lit continually when I have my truck and trailer lights on.

I also have a horse trailer with a seven pin connector and the lights on the horse trailer work as expected.

If you combine those two facts, it means that the problem is not in your tow vehicle but in the trailer mentioned first. If the problem was the truck, it would be the same in both trailers. When you connect the trailer and leave the lights off, do the brake lights work only when the brake is applied, or does the brake turn on both the brake and the taillight, like turning on the lights does?

 

[DonTom]

My brake lights are lit continually when I have my truck and trailer lights on. How do I attack this issue? Thanks in advance!

Are the truck brake lights on also? Extra bright? If so, I would start by checking the brake pedal switch.

-Don- Gold Run, CA

 

[Harry6082]

This happened to my sons vehicle. It turned out to be a spacer between the brake pedal and pressure switch that turns the lights on and off. Look at the brake stem holding the brake pedal and you should see where the stem presses that switch. See if the spacer has worn down allowing the lights to stay on.

Olly72, thanks, I’ll check it out. Harry

 

[Harry6082]

Are the truck brake lights on also? Extra bright? If so, I would start by checking the brake pedal switch.

-Don- Gold Run, CA

Thanks DonTom, I’ll check it out. Harry

 

[Harry6082]

If you combine those two facts, it means that the problem is not in your tow vehicle but in the trailer mentioned first. If the problem was the truck, it would be the same in both trailers. When you connect the trailer and leave the lights off, do the brake lights work only when the brake is applied, or does the brake turn on both the brake and the taillight, like turning on the lights does?

Kirk, thanks. Both brake and tail lights are on with the truck lights selected on. So, whenever someone is following me it appears that I am continuously braking. Not good. Harry

 

[DonTom]

Kirk, thanks. Both brake and tail lights are on with the truck lights selected on. So, whenever someone is following me it appears that I am continuously braking. Not good. Harry

Is the brake lights lit on the truck when the lights are off, with ignition on?

First make sure the truck's brake lights are working normally.

-Don- Gold Run, CA

 

[Kirk]

Both brake and tail lights are on with the truck lights selected on. So, whenever someone is following me it appears that I am continuously braking.

If I am reading your posts correctly, the problem you have is only with the RV and not with the horse trailer. If that is true, then the problem has to be in the RV. If the cause was the truck, it would do the same thing with anything supplied by it's plug. The second part of the question is, if you do not turn the truck lights on, do the brake lights then work properly and only light when brake is applied?

 

[gwinger]

The answer depends on the light type but often with traditional hot filament type lamps it's a ground problem Though ti's usually the tail's that light not the brake (higher wattage) element.

Bad grounds can cause some strange problems. Voltage back feeds through the filaments looking for a ground.

 

[mnmnutswer]

Weak brake pedal return spring..

 

[gwinger]

Weak brake pedal return spring..

If that were the case, it would also do it on the other trailer he hooked up.