How Does a Brake Controller Know when a Trailer is Connected

Question

Question:

Good morning, question is what signal is the brake controller receiving when trailer plug 7 wire is plugged into the vehicle

asked by: Marv

1

Helpful Expert Reply:

When a trailer with electric brakes is connected to a vehicle that has a brake controller that brake controller is sensing the draw of the brake magnets by sending back a small amount of voltage on the blue wire.

The brake controller also get's signals from the tow vehicle to let it know when you are stepping on the brake pedal. On most vehicles this connection is made either at the brake switch above the brake pedal or through some kind of tow package wiring.

I have included a link to our help article on brake controllers for you. It covers proportional and time delay controllers. If you are in a market for a controller I recommend a time delay such as the P2, # 90885. Proportional controllers activate the trailer brakes in proportion to how much the vehicle is braking using internal sensors. This is the safest way to stop and it reduces wear and tear on the vehicle and trailer.

expert reply by: Michael H

1

Jim W.

3/29/2020

I have a Hopkins Agility Brake Controller about 2 years old. The controller worked up to about a month ago indicating the trailer was connected. The red lamp that indicates this stoped working. The controller has voltage and ground from the battery and receiving voltage from the brake peddle. Blue wire good from the controller to the battery connections that stops a brake away trailer. Would one magnet cause the indicator to disappear or the brakes on the trailer to stop working?

Chris R.

3/31/2020

A bad brake magnet could be enough for the controller to sense a lost connection, since their draw is what is used to detect this. If you found that the brake magnet is bad, it certainly wouldn't hurt to replace it to see if it resolves the issue since it need to be done, anyway. Also check the power and ground wires coming from each brake assembly to make sure they're still securely attached - these (especially the ground wire) can come loose over time.

Alice

5/2/2024

I have no brake lights with no trailer connected, how can I fix that

Answer 1

The Hopkins 7-Way RV Style Trailer Connector with Nite-Glow - Trailer End #HM48502 will connect to your trailer wiring based on the function and pin locations of the attached photo. I've also attached an article to further assist with the trailer…

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Answer 2

Aftermarket brake controllers send a small amount of voltage along the brake output wire, if a trailer is connected, the magnets in the brake assemblies will create a power draw. This power draw tells the controller that a trailer is connected. The…

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Answer 3

The Dexter Nev-R-Adjust electric trailer brakes can be manually adjusted. There are a couple teeth of the adjustment wheel that are exposed just under the lever that you referenced. I have attached a photo showing the teeth. You will likely need a…

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Answer 4

In order to determine the torque rating for the lug nuts on your trailer you will need to know check out the chart I attached that shows all of the torque specs for all the trailer lugs available based on stud size, wheel material and wheel size.

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Answer 5

That's a very good question, we tend to be extra cautious and say to use 10 gauge wire because that would be more than enough. When you get into longer trailers that will end up using a lot of wire the heavier gauge wire becomes more necessary.…

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Answer 6

The torque for the Dexter Trailer Hub and Drum Assembly - 6,000-lb and 7,000-lb Axles - 12" - 5 Spoke Utility #8-174-5UC3 is not specified by the manufacturer. For 9/16 inch studs, the typical lug nut torque will be 120-140 ft lbs based on most…

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Answer 7

If you are only getting the 8 volts when you pull the pin using a meter like #PT89ZR, that has nothing to do with your brake controller as the breakaway battery is powering that from the trailer itself. You can confirm your brake controller is…

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Answer 8

If you are getting that low of a voltage reading to the 7-way of your tow vehicle I'd first try upping the voltage of the brake controller by increasing the output level of it to see if the voltage increases. It could be that the brake controller…

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Answer 9

There are many things that can affect the voltage on the brake output wire from your brake controller to your trailer brakes such as the power setting on your brake controller, how you are testing the wire and if you are testing it with the brakes or…

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Answer 10

Self-adjusting brakes like the etrailer.com Electric Brake Kit #AKEBRK-35-SA that you recently installed do require an initial calibration, which it sounds like you have already done. From there the brakes will continue to set themselves to the…

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Answer 11

On the Tekonsha Voyager brake controller, part #39510, there are seven levels of brake intensity. You will need to decide how much brake you want applied to your trailer in relation to the amount of brake you are applying in your vehicle. For…

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Answer 12

The adapter you need is the Valterra part #T1041-1 that you referenced as it fits your configuration needs. The 3 inch portion fits into the tank and then the 1-1/2 inch portion fits over the elbow fitting like you need. Rubber cement is basically…

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How Does a Brake Controller Know when a Trailer is Connected

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