EOH Brakes on New Trailer not Working With 2016 GMC 3500 With OEM Brake Controller

Updated 05/08/2017 | Published 05/05/2017

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LCD Digital Circuit Tester

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12-10 Gauge Butt Connector

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$0.86

10 Gauge Wire - Blue Primary - Per Foot

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Ring Terminal - 12-10 Gauge Wire - 3/8" Ring ID

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Question:

I have a brand new trailer with electric over hydraulic brakes. When you pull break-away switch brakes work. They dont work when hooked to my 2016 GMC, with factory installed gooseneck/5th wheel option, nor when hooked to either a Chevy or Ford trucks with after market controllers both of these trucks are used with other trailers with electric over hydraulic brakes and have no problem. I just got this Big Tx trailer and I have turned the gain all the way to 10 in my truck with no response to the trailer brakes. Have even tried plugging trailer into my sons Chevy, he had brakes applied showing 4.7 gain and I could move trailer as with no brakes working. When I stopped to ask dealer for ideas, they called Big Tx and was told to check truck wiring, hard for me to believe 3 trucks could be wired wrong how could they work on other electric over hydraulic brakes then?. Any ideas would be appreciated.

asked by: Larry

Helpful Expert Reply:

Since you have already tested the trailer brakes with a few different trucks by different manufacturers (2 of which have been used with an Electric Over Hydraulic (EOH) system), the problem should be with your trailer. The reason that they most likely recommended checking your trucks is that we have seen issues with OEM brake controllers from manufacturers working with EOH systems.

What you will first want to check is the connectors on both your 2016 GMC Sierra 3500 and your trailer. It would be highly unlikely that the connectors will have any rust or corrosion in or around either connector, but this is where you will want to start.

To make sure that you are actually getting a power signal from the connector on your trailer to the charger on your trailer you will want to connect the wires on the charger to a 12V battery and test the output from your charger using a Circuit Tester, like part # PTW2992, to make sure that you are actually getting a signal past your charger.

Next you will want to check the grounds on your trailer. Make sure to check the ground on your trailer connector, your breakaway system, and on the brake magnets. The grounds will need to be installed to bare metal areas that are clean and do not have any corrosion. You can also check the wiring that is connected to your brakes and your breakaway system to make sure that there are no places with bent or exposed wiring.

If you find any wiring that needs to be replaced you can use 10 Gauge Wire # 10-1-1 along with Butt Connectors # 05732-2 or Ring Terminals # DW05705-1 depending on what needs to be replaced.

If all of your wiring looks good then I recommend taking it to a qualified mechanic, or the dealer since it is brand new, and have them inspect it since they will be able to physically look at it.