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Hydrastar Troubleshooting Guide

by | Nov 10, 2023 | Repairs & Maintenance | 14 comments

Hydrastar Electric Brake Actuators are widely used for boat trailers with hydraulic brakes. If you are experiencing issues with your Hydrastar unit, you can troubleshoot it using various steps.

Troubleshoot: Hydrastar Not Working

  • Use the diagram provided to ensure the wiring is correct.
  • A 12-gauge cable is used to wire the unit.
  • Check all wires are correctly connected to the trailer plug and car socket.
  • Ensure there is no corrosion in the trailer plug and socket.
  • Ensure that the component is correctly ground via the white wire at the plug and not screwed directly to the trailer chassis.
  • Check that the unit is receiving power from the tow vehicle (black and blue wire from the actuator)
  • Ensure your tow vehicle is compatible via the compatibility chart.

If issues persist, conduct a battery test using the procedures below. If the actuator passes the battery test, the problem is not with the Hydrastar unit.

What if my Hydrastar is clicking?

One common mistake is having the blue brake controller wiring from Hydrastar wired into the brake-away. To test this, attach a yellow wire to the positive (+) terminal and a white wire to the negative (-) terminal.

If your brake-away system is fine, try following the advice above.

What if my Hydrastar has a delayed response?

Ensure that there is an adequate level of uncontaminated brake fluid. We recommend re-bleeding your trailer braking system (starting with the Hydrastar first).

Hydrastar Battery Test Procedure


Attach the BLACK wire to the positive (+) terminal, and attach the WHITE wire to the negative (-) terminal.

Hydrastar SHOULD NOT run
Attach BLACK and BLUE wires to the positive (+) terminal, and attach WHITE wire to the negative (-) terminal.Hydrastar SHOULD run

N.B. Use a 12 Volt battery source and isolate the wires from the Hydrastar when conducting this test.


  1. Shaun

    My brake controller wiring does not seem to match the wiring diagrams. The unit I have has two solid white wires, whereas the diagram shows a one white wire and one solid yellow (or blue with white stripe) wire.
    Can you please assist?

  2. Cam

    How do you release brake calipers without a brake roller in the the vehicle. We need to release the brakes of an empty trailer and do not have a tow vehicle with Brake unit?

    • Stephen

      Hydrastar have no park brake so it would appear you have sticky pistons that need replacing with stainless pistons. I am of course assuming you have hydraulic calipers. You will need to remove the calipers to move the trailer.

  3. Jim Walker

    Hydrastar clicks when brake controller activated and hums very quitely.
    Appears to work but very little if any braking pressure. Discs are rubbed but no noticeable braking.

    • Kate

      Hi Jim, it might be an issue with the wiring.

      Hydrastar units need to have seperate wires running from the brake controller and from the brakeaway switch. Often, we’ve found clicking occurs when the blue wire from the Hydrastar is wired to the brakeaway; whereas it should be for the brake controller. I’d recommend having a look at the wiring here and see if that may be the root cause.

      If that doesn’t help, feel free to give our team a call on 07 3348 3822!

  4. Paul Sedman

    Brakes come on but do not release. Lo ked on only release when hydrolic fluid pressure line released. Same scenario with different vehicles towing trailer. Ligts etc working fine.Is it the solenoid.

    • Stephen

      Hello Paul, Without looking in several areas, I could not provide a solution. One thought comes to mind, sticking pistons and/or slides.

  5. chris

    wiring correct, motor sounding correct– fluid leaking out when it should be powerful when bleeding. problem definitely in the sending of fluid from box. what do I need ?

    • Stephen

      Hello Chris,
      Your question is difficult to answer correctly without seeing th eunit but let’s see if I can help.
      1. Remove the hose from the hydrastar and power up the hydrastar to test for a blockage in the hose.
      2. Check the hydraulic fluid is full in the hydrastar.
      3. Check for leaks coming out of the hydrastar.

      Check the wiring negative is not connected to the frame of the trailer and is connected into the loom.

      If all good then the pump is cavitating and not producing pressure because you say the motor sound normal.

      If the problem is not identified above then replace the hydrastar.

      Thank you, Steve Wotherspoon

  6. Alan Coulton

    My brake controller was working, now when the pedal is applied the motor runs continuously and the brakes are not effective, can you help?

    • Stephen

      Hello Alan, There could be a number of issues here. Best take your trailer to a service mechanic for a quote.

  7. Robert Marchesi

    Why do the brakes come on when the controller is turned right down. Sometimes only one brake and sometimes two or three. Then sometimes they will be ok. Driving me crazy.

    • Stephen

      Hello Ian, It sounds like sticking pistons especially if they are phenolic type. A good investment is to change them over to stainless pistons. The older type piston is susceptible to scratching and absorbing moisture. This causes the piston to stick and not retract properly. Stainless pistons do not absorb moisture.


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