Dexter Electric Over Hydraulic Brake Actuator Pump Runs But Brakes Do Not Work  

Question:

Expert Reply:

You will want to start by following the troubleshooting tips in the manual for the electric over hydraulic actuator, # K71-651. I have outlined them here for you:

1. Verify that the trailer and tow vehicle are wired according to the electrical schematic shown in “Electrical Requirements”.
2. Re-bleed the trailer brakes. Any air in the trailer brake system causes brake delay
3. if the trailer is equipped with drum brakes, re-adjust the drum brakes to the trailer manufacturer's recommended running clearance.
4. Trailer wiring that is too small can cause slow response
5. Slow response can be caused by brake line restrictions. The trailer brake lines must be at least 3/16” in diameter. Steel tubing is preferred over flexible hoses.
6. Check to see if the white ground wire runs directly to the tow vehicle ground. IT MUST NOT BE GROUNDED TO THE TRAILER ONLY. IT IS IMPORTANT THAT THIS GROUND WIRE RUNS DIRECTLY TO THE TOW VEHICLE'S BATTERY GROUND. NO EXCEPTIONS.
7. Detach all wires from the Dexter Axle E/H unit leaving only the blue, black, white and yellow wires. It is important that the unit is disconnected from any other wires going to the towing vehicle or breakaway switch and breakaway battery. Failure to do so may result in a faulty test.
8. Using a 12 volt battery, connect the white wire to the negative (-) terminal of the battery.
9. Connect the black wire to the positive (+) terminal of the battery. The motor should not run. If the motor runs, the unit may be defective.
10. Leave the white wire connected to the negative (-) terminal of the battery.
11. Connect the blue and black wires together to the positive (+) terminal of the battery.
12. The motor should run and the unit should pressurize
13. If this does not occur, the unit may be defective.
14. Leave the white wire connected to the negative (-) terminal of the battery.
15. Connect only the yellow wire to the positive (+) terminal of the battery.
16. The motor should run and the unit should pressurize.
17. If this does not occur, the unit may be defective.
18. If the unit checks OK, reconnect the wires leading to the trailer plug and repeat steps 9 through 14 at the trailer plug. If you do not get the same results as before, the problem is in the trailer wiring or the electronic brake controller.

Using the breakaway system to troubleshoot a unit that is not operating correctly.

1. With a fully charged breakaway battery and trailer plug disconnected, pull the breakaway switch on the trailer.
1. If the unit runs and builds pressure, the breakaway system is functioning properly.
2. If the unit runs and builds pressure when the breakaway switch is pulled but will not function under normal operating conditions, the problem mot likely is a defective in-cab controller or defective wiring between the tow vehicle and Dexter E/H actuator.
3. If the unit runs but will not build pressure when breakaway switch is pulled, the Dexter E/H unit may be defective.
4. If the unit does not run, measure the DC voltage between the white wire and the yellow wire. If the voltage is less than 12 volts, either the breakaway switch or the breakaway wiring is defective.
5. After completing the above steps, reset the breakaway switch and reconnect the trailer plug.

Most of the time there is some wiring issue such as a loose connection or weak ground that causes problems. The other likely issue is that the brake controller is either not in electric over hydraulic mode or the controller is not electric over hydraulic compatible. This is the case with most factory integrated brake controllers. Switching to an aftermarket controller that is compatible, such as the P2, # 90885, would solve that issue.

expert reply by: Michael H

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