Troubleshooting Curt # C51120 Discovery Brake Controller Showing Flashing Decimal Point on Display


Dot flashing on controller when brakes pressed. No other message, with or without trailer. On 1976 Chevy c20


Expert Reply:

What you're describing sounds like it could either be an interruption in the trailer brake voltage output circuit, somewhere between the controller and the trailer brakes, or you could have a defective controller.

Use a circuit tester with an incandescent bulb, like part # 40376 and use the probe to pierce the insulation of the blue output wire exiting the rear of the controller and ground the alligator clip. Apply the brake pedal. If the load provided by the tester causes the display to illuminate normally, you've proven that there's a problem somewhere in the output circuit. Check the trailer connector on the vehicle for corrosion or damage and repair or replace as needed. Do the same for the connector on the trailer. Trace the blue wire back to the brake magnets, look for pinched wires or loose connections. Check the wiring connections at each brake magnet. One wire should be grounded to the trailer frame, the other connected to the brake output circuit.

Worn brake magnets would also be a possible cause. Pull your hubs and examine the face of the magnets that ride against the inside armature surface of the hub. If the face of the magnet is worn to the point where you can see the copper wiring showing through the face of the magnet, the magnet should be replaced.

If using the tester on that output circuit does NOT give you a normal display on the controller, the controller is defective and should be replaced. For a replacement, I'd recommend a proportional controller like the Tekonsha Primus, part # TK90160. A proportional controller provides safer, more predictable and efficient braking response.

You can see our brake controller troubleshooting FAQ article by clicking the provided link.

expert reply by:
Mike L

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