Will Trailer Lighting Circuit Still Work with 7-Way if Brake Controller isn't Used

Question

Question:

Will trailer lights still work when plugged into the 7-pin connector if I do not have a trailer brake installed yet?

asked by: Donnie D

0

Expert Reply:

Yes, the lighting functions of a trailer 7-way will be fully functional regardless of if a brake controller is installed/functional. The circuits are totally separate. There are many people who use 7-way trailer wiring setups without a brake controller and lighting all works fine.

expert reply by: Jameson C

0

Scott

2/26/2024

Is the 12v pin always expected to be working, even without a brake controller attached?

Reply

Jameson C.

2/26/2024

@Scott The 12 volt accessory circuit is totally independent from the brake controller so without one installed it could be active. I will say that it's not always active so it could just be not wired up.

Reply

Answer 1

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Answer 2

If Mercedes installed the factory brake controller harness on your 2016 Mercedes Sprinter Motorhome, it would be under the driver's seat. It would have a green connector. If the harness is not under the seat, then from our experience, it was…

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Answer 3

According to my research, if your 2017 Mercedes-Benz Sprinter 2500 came with a factory 7-way trailer connector then you will have the brake controller connector pre-wired. This pre-wired connector should be under the driver side seat which you can…

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Answer 4

Your brake lights and running lights are designed to be operated by two different circuits. You'll need to find the running light circuit in your trailer's wiring and then you'll need to run that circuit to the running light…

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Answer 5

I went out to the warehouse and grabbed a 7-Way Molded Trailer Wire Connector #H20046 to measure it for you. I used a set of digital calipers to get an accurate measurement. The diameter of the outer black sheath is 0.59 inches or 19/32 of an inch.…

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Answer 6

If you connect the trailer brake light circuit to the trailer brake circuit your brakes would lock up immediately since 12 volts is max braking voltage for trailer brakes. You'd need a brake controller that can vary voltage so that you can…

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Answer 7

Trailer brake magnets actually are not polarity sensitive. That means either wire lead can be the positive as long as the other wire is grounded.

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Answer 8

Sounds like you have a ground issue on your trailer. Ground problems normally show up when there is more draw on a system such as when you have the running lights on and then use another function like a turn signal or brake light but can show up…

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Answer 9

There are a number of reasons why the brakes on your trailer may not be working. Lets start with the easiest things to check. First, check the vehicle and trailer connectors for corrosion. This can cause a short inside the connector and the brake…

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Answer 10

That has to be a brake controller issue. Sounds like the controller is backfeeding the stoplight circuit it taps into as a signal wire with voltage which is then activating your brake lights. When this happens the brake controller is in need of being…

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Answer 11

You are correct, you should only be getting output when the brake is applied, or the override switch is activated. It sounds like the controller might be bad, but to make sure, you should probably bench test it before tossing it. Use a circuit…

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Answer 12

You will first want to check the fuses on your tow vehicle. Some vehicles could have fuses for operating the turn signals and brake lights of a towing package. You will want to check if they are installed and working properly. The next thing is to…

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Will Trailer Lighting Circuit Still Work with 7-Way if Brake Controller isn't Used

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