Troubleshooting Activator II Brake Controller Only Shows Dot when Trailer Connect to 2002 Dodge Ram

Expert Reply:

For the Activator II, # 5500, when the unit only displays the dot when the brakes are pressed and when the manual override is used means that there is no connection between the brake controller and the electric trailer brakes. On the brake controller, make sure the output is not at the lowest setting as this could cause this problem.

Next, check the blue wire coming out of the brake controller. Using a circuit tester like the Quickee # 3808, probe the blue wire and then step on the brake. If you do not get a signal, you might have the red wire connected to the wrong place on the stop light switch above the brake pedal. It needs to be connected to the wire that carries a signal only when the brake is pressed and at no other time. If you switch the red wire and that gives you a signal on the blue wire, test the manual override.

Next, try the manual override while probing the blue wire. If you get a signal but the trailer brakes still do not engage, test the vehicle side 7-Way for output from the brake controller. You will need to test the bottom right pin (if facing the 7-Way). If you do not get a signal then there is a problem somewhere in the vehicle wiring and you will need to follow the harness back to check for breaks in the wire, loose connections, and bad grounds.

If you are getting a signal at the 7-Way, then there is a problem on the trailer side wiring.

If you are not getting any output signal from the blue wire on the back of the controller, then the controller is bad and will need to be replaced.

You can also check the magnets on the brakes themselves. If a magnet is not grounded or has a bad ground, or if the magnet very worn, it might be causing problems.

expert reply by: Michael H