Weak Voltage At Brake Output Circuit On 7-Way Plug

Updated 09/11/2019 | Published 09/09/2019

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LCD Digital Circuit Tester

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10 Gauge Wire - Blue Primary - Per Foot

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Question:

Weak voltage at the back of the truck? For the trailer breaks only. 7 rv way plug

asked by: Kevin

Expert Reply:

First you want to test the brake output circuit on the 7-Way Plug with a circuit tester like part # PTW2992 with the manual override or brakes applied in the vehicle. If you are not testing the brake output circuit with either one of these activated you will not see the full voltage on the 7-Way which is what you want. If you are testing with manual override on the brake controller activated or the brakes depressed and are still getting weak voltage on the brake output circuit then there is an issue in the brake output wire somewhere between the brake controller and the 7-way.

Check the ground wire on the 7-way plug to make sure it is attached to a clean bare metal surface of the vehicle's frame. You also want to check the connections of the brake controller if it is hardwired. To check the brake controller you can sever the blue wire about 7 inches back from the brake controller. Test the blue wire from the brake controller for power. If you are getting power on the blue wire from the brake controller when the brakes are depressed then you know the issue is not the brake controller. If you do not get power from the brake controller then it needs to be replaced.

If you do get power then you know the problem is with the blue wire that extends back to the 7-way plug. You want to follow that wire back to the 7-way plug checking for any obvious signs of damage like frayed or split wires. You will need to replace any damaged wire with 10 Gauge Primary Wire - Blue - per Foot part # 10-1-1.

expert reply by: Heather A