I Have Little to No Braking at the Trailer Wheels

Updated 09/18/2013 | Published 09/16/2013

Question:

Tow vehicle...2003 Ford Expedition I have removed trailer wheels to check for bad drums, brake shoes and magnets. All in great shape. I have power to appropriate terminal @ the connector but only 3.6 volts with engine running and brake fully applied. Should it be a full 12 volts? Does this suggest a less than perfect ground? All other light functions are good through connector i.e. turn signals, clearance, headlights, and brakes. Your comments would be appreciated

asked by: Barry H

Expert Reply:

The 3.6 volts that you are reading at the trailer connector would be correct if you are using a proportional brake controller. Proportional brake controllers use an accelerometer to sense the braking intensity of the tow vehicle and sends an appropriate amount of power to the trailer brakes. If you are using a proportional brake controller, then try activating the manual override lever. That should send close to 12 volts to the trailer connector.

If you get 12 volts with the manual override, then I recommend adjusting the brakes. I have attached an electric brake installation video for you to check out. Our installer demonstrates how to adjust the brakes at the 1 minute and 55 second mark.

If you are using a time delay brake controller, then you should get the same amount of voltage that was set on the brake controller. If the brake controller is set to 7 volts and you are only reading 3.6, then the issue would likely be a poor ground connection.

One way to test to see if the brake controller is the issue is to cut the blue wire exiting the brake controller about 6 inches from the back of the brake controller. You can use your volt meter to make sure the correct amount of voltage is leaving the brake controller. If the brake controller was hardwired, you may also want to check the ground for the brake controller before testing.

If you are unable to find the issue or come up with a solution after following these steps, let me know what you come up with and we can take further steps.

expert reply by: John H