Troubleshooting Electric Over Hydraulic Brakes On 40 Ft Trailer With Dexter Actuator

Question:

Hello i have a 40 foot with 10k alko drums and a dexter pump. For some reason the brakes have a major delay in them. I have bled them several times and nothing works. The front axle will lock while going forward but not backwards and the rear axle will lock up backwards but not forward. I am really at a loss here. Please let me know what you think thank you.

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Expert Reply:

The first thing I recommend is to check the brakes you have on your rear axle. It sounds like they are possibly reversed left to right hand. That would cause the problem you are having with them locking when in reverse and not forward. It sounds like the front brakes are acting correctly since they are designed to allow you to back up without locking up as you mentioned.

Next, I recommend testing the breakaway switch. With the breakaway battery fully charged and the trailer plug disconnected, pull the breakaway switch. If the unit runs and builds pressure, the system is running properly.

If it runs with the breakaway switch pulled but does not work under normal conditions, the issue is either a bad brake controller or the wiring between the truck and the actuator.

If the unit runs but will not build pressure with the switch pulled, the actuator may be defective. If the unit does not run, check the voltage between the white wire and the yellow wire. If the voltage is less than 12 volts, either the breakaway wiring is defective or the breakaway switch is bad.

If the brakes are extremely slow to respond there may be something blocking the lines or possibly the lines are too small, and not allowing enough fluid through. The lines should be 3/16 inch diameter at minimum.

Check the ground wire connections on the trailer. They should not be grounded to the trailer only. They should be connected to the ground wire on the connector that is attached to the battery ground.

1) 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. Using a 12 volt battery, connect the white wire to the negative (-) terminal of the battery.

2) 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. Leave the white wire connected to the negative (-) terminal of the battery. Connect the blue and black wires together to the positive (+) terminal of the battery.
The motor should run and the unit should pressurize. If this does not occur, the unit may be defective.

3) Leave the white wire connected to the negative (-) terminal of the battery. Connect only the yellow wire to the positive (+) terminal of the battery. The motor should run and the unit should pressurize. If this does not occur, the unit may be defective.

4) If the unit checks OK, reconnect the wires leading to the trailer plug and repeat steps 1 through 3 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.

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Jeffrey L

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