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Wayne
Wayne, Journeyman
Category: Medium and Heavy Trucks
Satisfied Customers: 8902
Experience:  worked on, Gmc, Macks, Freight liner,Mercedes Benz,,Ford, sterling
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I have 2007 Freightliner Classic. I am having a problem with

Customer Question

I have 2007 Freightliner Classic. I am having a problem with the brake lights staying on after an application. This ONLY happens when connected to a trailer?? Tractor is fine when bob tailing. I have replaced the brake light switch, but then realized it was only happening when connected to a trailer? Any thoughts would be appreciated. Thanks
Submitted: 6 months ago.
Category: Medium and Heavy Trucks
Expert:  roybelding replied 6 months ago.

good afternoon my name is ***** ***** I will assist

did you check the brake light switch on the trailer??? when hooked to a trailer, there is a brake light switch for the tractor and one for the trailer.

Roy

Customer: replied 6 months ago.
Hmmm. No I didn't. Would it be close to the tractor one? Will it look identical?
Expert:  roybelding replied 6 months ago.

it is part of the trailer. you would have to look around for it on the trailer. location varies according to manufacturer.

yes, it looks the same

Customer: replied 6 months ago.
The tractor is hooked to as many as a dozen trailers everyday. They can't all have brake light switch problems? I don't know of any trailers with brake light switches? Signal originates in tractor and goes through light cord?
Expert:  roybelding replied 6 months ago.

yes, trailers have these switches. there is 12 volts supplied from the tractor to the switch and then air pressure completes the circuit and turns on the lights.

I agree with all the trailers. check the output at the tractor for voltage to the trailer. check all the fuses at the top of the dash on passenger side as well as behind the drivers seat.

Roy

Customer: replied 6 months ago.
The brake lights are working on all the trailers. Don't think it is a power problem as far as fuses? It's just that the brake lights are staying on? It happens with every trailer so it has to be something in the tractor. Is there perhaps a module or something on the tractor for the trailers?
Expert:  roybelding replied 6 months ago.

no there is not.

I will opt out and re post for you to see if anyone else has any other ideas

Roy

Customer: replied 6 months ago.
Thanks
Expert:  Wayne replied 6 months ago.

Hi I'm Wayne

I will try to help you with this

is this a M2 F/L

Customer: replied 6 months ago.
Hi Wayne. It is an FL
Expert:  Wayne replied 6 months ago.

Thank you for that

look under the truck on the frame rail

see if you have a electric box with modules and air lines

Customer: replied 6 months ago.
Hi Wayne. I won't see the truck untill next week now.
Expert:  Wayne replied 6 months ago.

HI

OK , that is fine

just between you and I and the gate Post , worked 34+ years as mechanic,

never seen a stop light switch on a trailer, not saying there is not, but I have never seen one

Customer: replied 6 months ago.
Lol. Thank you!!!!
Expert:  Wayne replied 6 months ago.

LOL

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