Troubleshooting Electric Over Hydraulic Trailer Brakes Jerking When Brakes are Quickly Applied  

Question:

Expert Reply:

A lot of things could be going on here. First, I would make sure that the P3 brake controller is set to Hydraulic mode, see instruction link (page 4, Set Brake Type section). If it is still in the electric mode that is most likely the issue.

Next, you might have an intermittent power supply to the EOH (electric over hydraulic) controller on the trailer. Check the voltage display on the P3 brake controller and if the readings are all over the place then the brake output wire should be checked all the way through the connectors to the EOH unit. You may find that corrosion in the connector on the truck or trailer is the issue, or that you have a broken or pinched wire somewhere that is showing up when maximum output is applied.

Next, check the ground connections for the electric over hydraulic unit, brake controller and trailer connectors. If you have a bad ground this could be causing the intermittent application of the brakes when full amperage is applied on the system, see video link. Check the trailer connectors inside and out.

Next, the EOH controller could have air in the hydraulic system causing pressure to spike and drop. This would cause the brakes to activate and release causing the jerking you are experiencing when the brakes are applied quickly.

Finally, the disc brake calipers may be hanging up and releasing causing the jerking, you should inspect the brakes on the trailer.

expert reply by: Robert G

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