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This electric-over-hydraulic actuator gives you full control of your trailer’s hydraulic drum brakes right from your brake controller. Instead of waiting for the trailer to push against a surge coupler, the Hydrastar responds instantly when you hit the brakes. The electronic, proportional pressure valve delivers smooth, even braking at up to 1,000 psi, and the manual override on your brake controller lets you apply the trailer brakes independently when you need to slow things down on a hill or while backing up.
The large 32 oz reservoir is built to handle long brake lines and multi-axle trailers that need more fluid volume. The translucent tank makes it easy to check levels at a glance, so you always know your system is ready. A built-in bleeder screw helps you purge air from the lines quickly, keeping pedal feel firm and braking performance consistent every time.
The durable extruded aluminum body resists corrosion and stands up to wet or marine environments. Since it’s made for frame mounting, it stays protected yet accessible for wiring and maintenance. The 12V DC motor and high-quality seals are designed for dependable operation season after season—no rust, no sticking pistons, just reliable braking power.
This actuator ties right into your existing electric brake controller using standard color-coded wiring—black for 12-volt power, blue for the controller signal, yellow for breakaway, and white for ground. It’s compatible with any standard 5-amp-hour-battery breakaway kit (sold separately), so if your trailer ever separates from the tow vehicle, the brakes engage automatically.
Installation is straightforward—mount it on the trailer frame, connect the 3/16" hydraulic port, and wire it up. The translucent reservoir and external bleeder screw make upkeep simple. DOT 3 or 4 fluid keeps things running smoothly, and since everything is sealed against dirt and moisture, you can count on consistent performance every trip.

Do not power wash the Hydrastar actuator or take it through a commercial car wash. High-pressure water may damage the seals on the actuator.
Videos are provided as a guide only. Refer to manufacturer installation instructions and specs for complete information.
Hello, everybody, this is Jeff at etrailer.com. Today, we're gonna take a look at the Hydrastar Electric Over Hydraulic Actuator for drum brakes. Has a 32 ounce capacity and a 1,000 psi output pressure. Now, with a huge reservoir that holds a full quart of fluid, this actuator's perfect for your big multi-axle camper. Application, will fit single tandem and triple axle trailers with drum brakes. It is an electric over hydraulic brake actuator, so it does activate your trailer's hydraulic drum brakes when you apply the brakes in your tow vehicle.
A brake controller is required to send that signal from the tow vehicle to the actuator when your brakes are applied. The brake controllers we do sell separately. Also, you'll need a 7-way trailer connector, and that's needed to transmit the signal from the brake controller. This will give you improved functionality when compared with surge brake couplers, 'cause it'll give you a faster response time. Your trailer brakes are triggered when you apply the brakes in the tow vehicle as opposed to when the trailer pushes against the hitch ball.
There's no need to manually lock out your brakes when you back up, and the trailer brakes can be intentionally activated when you reverse. The manual override on the brake controller can be activated, so that you can engage the trailer brakes without having to apply your vehicle brakes. As we mentioned, this has a huge reservoir. It's great for trailers with long brake lines that need high volumes and brake fluid. As we mentioned, this has a fluid capacity of 32 ounces.
Right up at the top here, you'll notice it is a translucent tank, and that lets you check the fluid level at a glance. Now, it does require DOT 3 or DOT 4 brake fluid. It is not included, you would have to supply that. They do use an electronic proportional pressure valve to ensure that the braking is smooth and effective. Right up at the top here, has a built-in bleeder screw, which will let you easily flush out air of the brake lines.
And right down here is where your brake line attaches. As you can see, this is a nice, durable, extruded aluminum construction, provides corrosion resistance. And it is compatible with any standard five amp hour battery breakaway. This unit will install on your trailer frame, connects to your trailer's wiring and the hydraulic brake line. The brake lines we do sell separately. This part is made in the USA. Power for this is 12 volt DC power. The maximum output pressure is 1,000 psi. It is DOT, Department of Transportation compliant. We mentioned it connects to your trailer wiring. And if we pull out our wires here just to show you, there's four wires. And basically, the black one is for your 12 volt power, the blue one is for your brake controller, yellow is for your breakaway, and the white is for the ground. And the last thing, just give you the mentions on this. If we measure the length, if you noticed at the bottom, it has this mounting tabs. So we're gonna measure from the edge of the mounting tab to the edge of the mounting tab. So if we do that, that's gonna be right at 11 3/4 inches long. The width, the widest point, right at three inches wide. And the height from the bottom to the top of the cap here is gonna be right at 10 3/4 inches tall. But that should do it for a look at this Hydrastar Electric Over Hydraulic Actuator for drum brakes.
Ratings & Reviews

Scott K.
5/12/2021
Super!

Katrina B.
5/11/2023
It seems that the manufacturer prefers to handle all warranties. Lets get you their information via email.

Heather A.
10/9/2020
Thank you for your review. The Hydrastar Actuator will wire to the breakaway kit of the Kaufman trailer and the electric brake controller in the tow vehicle. I have attached an electrical diagram for a visual of how the wires attach. You should already have a brake controller for the electric brakes but if you have an OEM brake controller it will need to be replaced. I recommend the Prodigy P3 90195 which is one of our most popular brake controller options. If you need a breakaway kit, I recommend Hopkins engager break away kit part 20099 because of its convenient push to test button and built in charger.
Helpful Links
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James
4/12/2019
I am happy with the actuator and how well it is working

John B.
10/23/2013
Have Hydrastar HBA12 1200psiG7 on tandem boat trailer. Breakaway activates brakes well but brakes activated thru vehicle do not work.A check of power from vehicle to trailer indicates circuits are all good. Can hear contact noise from inside brake unit but pump doesnt start but thru breakaway activation the pump works well.Have been told the fault is in the Electronic Chip that activates the pump. Is this correct and if so can I purchase that part only? What part number do I order? Appreciate your reply. John B

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Frank C.
5/8/2022
Juste great, as new