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Why are My Trailer Brakes Losing Power?

Question:

I'm just trying to find the trailer brake wire behind the bumper. The wires that are actually going to the 7pin. I was hoping to get a pic of a diagram for all those wires and harnesses that are behind the bumper. Or maybe a color? I apologize for not mentioning that!

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Expert Reply:

One thing to do to troubleshoot your issue with the brake wiring is to make sure that you are getting power from the vehicle's 7-way to the braking pin on your trailer's 7-way connector. I went ahead and attached the diagrams of the pin setups on different styles of 7-way connectors. If you need a circuit tester, I recommend part # 40376. It is possible that there are some frayed wiring and some corrosion at the pin location as well. When testing this circuit, it is important to use the manual override on the brake controller instead of simply stepping on the brake pedal.

As far as the wire that connects to your trailer's brakes from the trailer's 7-way, I went ahead and attached a diagram that shows the wiring setup for the wiring that goes to both sets of brakes. As you can see, the blue braking wire should not affect the brake lights of the trailer in any way. With that being said, if you are having trouble with the driver's side brake lights, that is a separate issue from the brakes. You will need to go through the process of checking for wire fraying and corrosion in the connector as well.

7-Way Pin Setup on Trailder Side
7-Way Pin Setup on Trailder Side
(click to enlarge)
7-Way Pin Setup on Vehicle's Side
7-Way Pin Setup on Vehicle's Side
(click to enlarge)
Wiring Diagram
Wiring Diagram
(click to enlarge)
expert reply by:
0
Bob C

Question:

One thing to do to troubleshoot your issue with the brake wiring is to make sure that you are getting power from the vehicle's 7-way to the braking pin on your trailer's 7-way connector. I went ahead and attached the diagrams of the pin setups on different styles of 7-way connectors. If you need a circuit tester, I recommend part # 40376. It is possible that there are some frayed wiring and some corrosion at the pin location as well. When testing this circuit, it is important to use the manual override on the brake controller instead of simply stepping on the brake pedal. As far as the wire that connects to your trailer's brakes from the trailer's 7-way, I went ahead and attached a diagram that shows the wiring setup for the wiring that goes to both sets of brakes. As you can see, the blue braking wire should not affect the brake lights of the trailer in any way. With that being said, if you are having trouble with the driver's side brake lights, that is a separate issue from the brakes. You will need to go through the process of checking for wire fraying and corrosion in the connector as well.

0

Expert Reply:

Not a problem! I went ahead and attached the wiring diagram of the 7-way wiring from the vehicle's side and from the trailer's side. Also, for your convenience, I went ahead and attached photos of the pins that are on the vehicle's 7-way as well as the trailer's. The images are attached to this answer.

7-Way Pin Setup on Trailder Side
7-Way Pin Setup on Trailder Side
(click to enlarge)
7-Way Pin Setup on Vehicle's Side
7-Way Pin Setup on Vehicle's Side
(click to enlarge)
Wiring Diagram
Wiring Diagram
(click to enlarge)
expert reply by:
0
Bob C

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