Troubleshooting Trailer Brake System That is Only Showing 5-Volts at Trailer Connector
Question:
poor trailer brakes. emergency slide works and hard/soft adjustment works, but the brakes dont work very well. Voltage at the electric brake contact only goes to 5 volts with foot pedal down and emergency lever pushed to full on. Is 5 volts enough or should it be more or 12 volts?
asked by: Mark T
Expert Reply:
With the brake controller gain turned all the way up, you should be seeing closer to 12-volts at your trailer connector. You are losing voltage somewhere between the brake controller and the trailer connector. I am assuming that by electric brake contact, you are speaking of the brake voltage output pin on the trailer connector.
Make sure your controller is properly installed and leveled according to the instructions. Use your tester on the blue brake output wire at the rear of the brake controller, and verify that you are getting 12-volts exiting the controller with the gain turned up to maximum and the manual brake switch applied.If you are getting significantly less than 12-volts at the rear of the controller, test the black wire feeding power into the controller. If you have 12-volts going in on the black wire, but less than that going out on the blue wire, the controller is bad and needs replacing.
Since you said that you are only getting 5-volts at the connector pin, test the blue wire behind the trailer connector. Once again, you should be seeing close to 12-volts.
If you are getting good voltage at the rear of the connector but not on the pin itself, check the trailer connector for corrosion. If you see any green or white corrosion on the pins, there is a good chance that the corrosion has spread to the interior of the connector, and is preventing full voltage from being passed on to the trailer. Replace the connector as needed.
These are the most common culprits that would cause the problem you described. I have provided links to our Brake Controller FAQ page, as well as a video showing the procedure for bench testing a brake controller.
Product Page this Question was Asked From
4-Way Flat Trailer Connector w/ 72" Harness, Circuit Tester and Wire Taps
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- No Converter
- 6 Feet Long
- Universal Fit
- 4 Flat
- Tekonsha
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