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  1. Trailer Brake Controller
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  3. Electric
  4. Proportional Controller
  5. Indicator Lights
  6. Up to 3 Axles
Hayes Energize III+ Trailer Brake Controller - 1 to 3 Axles - Proportional

Hayes Energize III+ Trailer Brake Controller - 1 to 3 Axles - Proportional

Item # HA81742B
Our Price: $91.23
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Trailer Brake Controller
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Product Expert Kathleen M

Is this right for you? Product Expert Kathleen M says:

Yes, if you:

  • Worry about premature brake wear which is less likely to happen with a proportional brake controller
  • Only tow occasionally and don't want to pay a bundle for a controller you won't use often
  • Prefer products that are made in America

No, if you:

  • Tow often and need something a little more user friendly
  • Have limited room between your knees and the dash of your tow vehicle
  • Have a trailer with hydraulic brakes or more than 3 axles
This proportional brake controller keeps towing simple with a straightforward design and user-friendly controls. Includes an LED indicator and a slide-bar manual override. Adhesive backing gives you the option of drill-free mounting. Great Prices for the best trailer brake controller from Hayes. Hayes Energize III+ Trailer Brake Controller - 1 to 3 Axles - Proportional part number HA81742B can be ordered online at or call 1-800-940-8924 for expert service.
  • All Info
  • Reviews (61)
  • Q & A (0)
  • Photos
  • Why etrailer?

Hayes Trailer Brake Controller - HA81742B

  • Electric
  • Proportional Controller
  • Indicator Lights
  • Hayes
  • Up to 3 Axles
  • Under-Dash Box
  • Dash Mount

This proportional brake controller keeps towing simple with a straightforward design and user-friendly controls. Includes an LED indicator and a slide-bar manual override. Adhesive backing gives you the option of drill-free mounting.


  • Brake controller activates your trailer brakes in proportion to your vehicle's braking action
    • Automatically adjusts trailer's braking based on deceleration of tow vehicle
  • Simple controls keep your settings within easy reach
    • Gain setting lets you adjust the amount of power sent to the trailer's brakes
    • Slide-bar manual override allows you to control trailer sway or stop in emergencies
    • Deceleration sensor lever lets you adjust initial braking power and aggressiveness for smooth, safe braking
  • Red LED indicator lights up when brakes are engaged
  • Quick, simple installation with included bracket and hardware
    • Drill-free installation option with included adhesive tape
    • Optional universal wiring adapter (HA81789-HBC) sold separately for a plug-and-play installation
    • Plug-in, vehicle-specific brake control adapter (sold separately) can be used to reduce installation time on certain vehicles
    • -35-Degree to 90-degree mounting range - must be horizontally level
  • Made in the USA


  • Application: trailers with up to 3 axles (6 brake assemblies)
    • Compatible with electric brakes only
  • Dimensions: 5-3/8" long x 3-1/4" wide x 1-3/8" tall
  • Mounting angle: -35 degrees to 90 degrees vertically
  • 5-Year limited warranty

Gain Setting for Braking Power

You can adjust the gain setting (also known as braking output) on the Hayes Energize III+ using the thumbwheel on the front of the module. This will set the maximum amount of power that will be applied to your trailer's brakes. You want to go as high as you can without the trailer brakes locking up. Typically, the gain is only readjusted when you experience changing road conditions or if you switch over from a heavy, loaded trailer to a much lighter, empty trailer, or vice versa. To get more power to your brakes, turn the wheel up. To get less power to your brakes, turn the wheel down.

Hayes Energize III+ Braking Output

The red LED indicator on the front of the module will light up when the brake controller is activated. This way you can keep your eye on your braking and be sure that it's working.

Sensitivity Adjustment with Deceleration Sensor Lever

Once you have the overall power set, you can fine-tune the power output by adjusting the sensitivity of the internal sensor. This controls the aggressiveness of your trailer's braking, meaning how quickly the brakes reach the maximum braking level. You can adjust this when you're towing heavy loads and you need more umph to bring your trailer to a stop. Your tow vehicle doesn't need that much power to brake in time, but your heavy trailer does. Boost gets the braking power to your trailer brakes faster and with more intensity so that it doesn't push your tow vehicle forward. To increase the sensitivity for towing heavier loads, move the lever away from you. For a lighter load, move the lever toward you.

Slide-Bar Manual Override

The Hayes Energize III+ comes with a built-in, easy-to-reach slide-bar manual override, great for stopping sway or controlling your trailer's momentum in emergencies. To engage the manual override, just push the slide-bar to the left, toward the center of the controller. This will activate the trailer's brakes and brake lights without you having to apply the brakes on your tow vehicle, perfect for limiting trailer movement while you're cruising.

Quick, Simple Installation

The Hayes Energize III+ is easy to mount wherever you want it. Simply use the bolts or the double-sided tape to secure the included mounting bracket to your dash, and then install the controller in the bracket.

If your vehicle already has a plug-in brake controller wiring harness, just connect the unit to it. Otherwise, you will need to purchase a vehicle-specific wiring harness (sold separately) to plug into. If a harness is unavailable for your vehicle, hardwiring will be necessary.

Because the Hayes Energize III+ operates with an internal inertia sensor, it must be mounted between -35 degrees and 90 degrees vertically. The brake controller also needs to be horizontally level and parallel with the direction of travel to function properly.

Hayes Energize III+ review

Installation Accessories

See's exclusive 7- and 4-way brake-control installation kit (ETBC7 - sold separately) if you don't already have a 7-way plug at the back of your vehicle

Note: One of the following will be required to ensure proper installation:

  • 20-Amp circuit breaker (9506P - sold separately) for 2- to 4-brake applications
  • 30-Amp circuit breaker (38630 - sold separately) for 6- to 8-brake applications

Proportional Braking

What is proportional Braking

The Hayes Energize III+ brake controller comes equipped with proportional braking to give you the best towing experience. Proportional braking means that your trailer brakes mimic your tow vehicle's brakes. If you slam on the brakes in your vehicle, your trailer brakes will activate with the same intensity; if you brake lightly, your trailer brakes lightly too. The trailer's braking is in proportion to your vehicle's braking. This saves wear and tear on the tires and the brakes on both your vehicle and trailer.

The Energize III+ uses a pendulum system to sense how your vehicle is braking so it can send the right amount of braking power to your trailer. It detects the inertia of your tow vehicle and activates the trailer's brakes to slow at the same rate. The result is uniform braking across your towing setup. No push-pull action - just smooth, proportional braking every time.

81742B Hayes-Lemmerz Energize III Plus Brake Controller - 1 to 3 Axles - Proportional

Replaces 81741B and 81745

Installation Details HA81742B Installation instructionsAlternate Instructions HA81742B Installation instructions

Customer Satisfaction Score:

Customer Reviews

Hayes Energize III+ Trailer Brake Controller - 1 to 3 Axles - Proportional - HA81742B

Average Customer Rating:  4.6 out of 5 stars   (61 Customer Reviews)

This proportional brake controller keeps towing simple with a straightforward design and user-friendly controls. Includes an LED indicator and a slide-bar manual override. Adhesive backing gives you the option of drill-free mounting.


2001 Ford F-250. Plug and play. EASY!


Nicole was outstanding in knowledge and patience with me. She helped me get through my mistaken order and get me the right brake controller and adaptor harness for my truck. I installed it in less than and hour and it is working great. She also made the return of the controller and harness a breeze.


Remember the adage, "you get what you pay for"? Certainly applies here...I will never know if this unit was faulty when I received, or if it simply is poor quality. But the "gain" function on it does nothing, and therefore I can't dial in the sensitivity that is needed. Again, I don't know when/how it became inoperable, but I just ordered it's replacement. Am hopeful for a better experience...

This controller does have a limited lifetime warranty against manufacturer defect. Customer Service will be in touch.
-- Etrailer Expert Jenny N - 11/16/2022


This brake controller has worked great no problems at all I would recommend it to anyone using this style of brake controller.


This controller was truly "plug&play". Installation was 30 min. Works perfectly. E-trailer has always been my go-to for all my truck and camper needs!


I've used this a few times now on my '16 Crosstrek and have had no issues


This is a quality product. Before we purchased, we investigated a number of controllers and found Hayes had a great reputation and Hayes is MADE IN AMERICA
Y'all know there less expensive competitors out there with good reviews. Inhave no qualmspaying more for our country.






Arrived sooner than expected. Install was a breeze haven't used it yet so will update afterwards


Best of the four brake controllers I've had so far in my truck. Easy to adjust on the fly if brakes are too strong or weak. Manual override felt solid unlike some controllers out there. The instructions could've been written a little clearer though. 4 prong square plug also fits Curt controllers if swapping. Overall nice controller for the money, should've bought this one first and saved the cash


Doesn’t have all the bells and whistles of the higher priced competition but does a great job. Works flawlessly and the install was super easy.


5 minute install on my truck. Works just fine. I opted for standard shipping which I thought was expensive and took to long to receive.
Customer service is very good.


super easy to install with the adapter. gain was set a tad high initially so be sure to turn it down first, then up until you get the gain you want.

Working well, I now have it in a different truck.
Dennis p - 08/16/2021


Easy install harness worked perfectly


Used as a replacement everything went g reat


Got tip off Utube for the wiring harness adapter for a 2019 Ram. Installation was plug and play. We have a 26 ft camper we will be towing. Very easy install.

Great! No complaints.
Richard - 10/29/2020


Just what I was looking for. Bought the wire harness adapter with it and everything just plugged in and worked.


Working good


Very pleased with the Hayes controller and the installation videos and information available at etrailer. My installation was hardwired due to an earlier install which removed a connector, so etrailer support was very beneficial plus their price was very competitive...a winning combination.


Great Customer service!


Easy to assemble and etrailer made sure that I had everything I needed to install the brake control system. Order arrived on time and will definitely order from etrailer again.


Great job, fast shipping


Though I haven't had a chance to use the brake controller yet I'm sure it will be fine and if not I'm also sure etrailer will do anything they can to help.


Easy installation 5 minutes

Install was easy. Works as advertised
Howard - 04/27/2021

Show More Reviews

See what our Experts say about this Hayes Trailer Brake Controller

  • Hayes Blackbird Has Constant Power On Blue Wire Without Brake Pedal or Override Activated
    Correct, if you have constant power on the blue brake output wire then your brake controller is faulty and will need to be replaced. The Hayes Blackbird Trailer Brake Controller part HA81726 is a timed delayed brake controller so this would be a great time to upgrade to a proportional brake controller which will be much smoother and will have a faster response time. The Hayes-Lemmerz Energize III part # HA81742B would be a good option for this and it uses the same plug and mount you have...
    view full answer...
    Image 1 for
  • Where do Wires of Hayes Energize III Brake Controller Need to Run To
    For brake controllers like your Hayes Lemmerz Energize III part # HA81742B the white wire gets grounded, the black wire runs to a constant 12 volt power source, the red to a wire that only has voltage when brakes are applied (normally on the brake pedal switch), and the blue to the output circuit of the 7-way connector.
    view full answer...
  • Troubleshooting Hayes Trailer Brake Controller LED Flashing While Driving With Camper
    The LED light on your Hayes Trailer Brake Controller comes on when it senses power from the brake light switch or the controller is manually activated. Your brake light switch on your 2015 Nissan Pathfinder may be faulty. Since it is just blinking it does not see the power long enough to activate the trailer brakes. Since you have a 2nd Hayes controller on your other vehicle I would recommend swapping them to see if the same issue occurs with the other controller. This will tell you...
    view full answer...
  • Tips for Finding Brake Controller Stoplight Circuit Wire in Truck
    All you need for the red wire of your brake controller is a circuit that sees voltage only when the brakes are applied. If you wanted to run a wire to the fuse box to find a wire like you said that would work fine. Some people will also use the third brake light circuit as well. It almost sounds like you are running the blue wire of the controller to the stop light circuit if the brakes lock up when you tap them. Or your brake controller is just set too aggressively. I attached a help...
    view full answer...
  • Does Install of Brake Controller in a Vehicle Affect Vehicle Brakes
    The brake controller you sent in a picture of will only affect the brakes of a trailer you would be towing. It does not affect the brakes of your vehicle in any way if you were to leave the controller installed. I attached an FAQ article on brake controllers for you to check out as well.
    view full answer...
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  • Will Hayes Energize III Work on Tandem Axle Trailer with One Brake Axle
    The Hayes Energize III brake controller part # HA81742B that you referenced will work great on a tandem axle trailer that has one brake axle. That means your trailer has two assemblies which is perfect with this controller.
    view full answer...
  • Does The Red Indicator LED On Hayes Energize III Activate When The Trailer is Disconnected?
    Yes, the red indicator light will illuminate on your Hayes-Lemmerz Energize III+ Electric Trailer Brake Controller # HA81742B when either the brake pedal is pressed or when using the manual override. This will happen both when disconnected from a trailer or connected.
    view full answer...
  • What Does The Lever On The Side Of Hayes-Lemmerz Energize III+ Electric Trailer Brake Controller Do?
    The lever on the side of the Hayes-Lemmerz Energize III+ Electric Trailer Brake Controller # HA81742B allows you to adjust the proportioning of the brakes on the trailer. I have linked the instructions below that cover setting this lever to the correct position when installing.
    view full answer...
  • Brake Controller Wiring Harness for 2017 Ford Expedition
    Not all manufacturers will utilize the same brake controller wiring harness. Hopkins, Tekonsha, Curt, etc, all have their own connections on the brake controller side and the vehicle manufacturers will have a specific connector if they are prewired for a controller as well. For instance the Hayes-Lemmerz Energize III+ Electric Trailer Brake Controller - Proportional # HA81742B will use the Custom Wiring Adapter for Hayes Brake Controllers - Dual Plug # HA81794-HBC for a 2017 Ford Expedition....
    view full answer...
  • Harness Needed To Install Hayes Trailer Brake Controller On a 2020 Toyota Sequoia
    In order to install the Hayes-Lemmerz Energize III+ Electric Trailer Brake Controller part # HA81742B on a 2020 Toyota Sequoia you can use the Custom Wiring Adapter for Hayes Brake Controllers part # HA81785-HBC so long as you have the factory tow package. If you don't have the factory tow package you will need to hardwire the unit, let me know if this is the case.
    view full answer...
  • Can Hayes Energize III Install in 2001 Dodge Ram 1500 ST 4X4
    For your 2001 Dodge Ram 1500 the Hayes Energize III part # HA81742B that you referenced can be installed if you use the install harness part # HA81782-HBC that you referenced as that is the custom fit harness designed for your truck.
    view full answer...
  • Troubleshooting Brake Controller Installation on a 2011 Ram 2500 with OEM Controller
    When you're installing the Hayes controller, like the Energize III+ # HA81742B, on your 2011 Ram 2500 you should be able to install it by using the Wiring Adapter # HA81795-HBC. This plugs into the existing factory plug so you won't have to do any splicing with your wiring. If you're disconnecting wires and splicing the brake controller in then that may be why you're experiencing this. Under normal circumstances a brake controller should not be affecting the tail lights on the vehicle...
    view full answer...
  • Troubleshooting Energizer III Brake Controller with no Power Output on 2009 Chevrolet Silverado
    Yes, the signal for the trailer brakes comes from the stop light lead. The red wire on the controller is meant to be connected to the stop light circuit which is the light blue or orange wire on GM vehicles with the factory tow package. This wire will then send a signal to the brake controller when the brake pedal is pressed which in turn sends power to the trailer. I would first start off by testing the light blue stop light wire on your 2009 Chevrolet Silverado. You will want to use...
    view full answer...
  • Red Light on Hayes Brake Controller Stays on and Drains Tow Vehicle Battery
    I am not sure which Hayes brake controller that you have, but in reviewing the installation instructions for the Hayes-Lemmerz Energize III+ Electric Trailer Brake Controller # HA81742B I found that there is a section that goes over if the "Controller red indicator on all the time." The solutions they offer call for testing the Red wire and the Blue wire on the brake controller with a circuit tester like part # PTW2992. The Red wire connects to your Stop Light Switch and only receives...
    view full answer...
    Image 1 for
  • Will Curt C51180 Echo Brake Controller Override Existing Aftermarket Brake Controller
    That's an excellent question! The Curt # C51180 Echo wireless trailer brake controller will work with your aftermarket brake controller installed. The Echo gets all its inputs from the 7-way trailer connector, bot the brake lamp circuit and the 12V power for the trailer brakes, so once you plug it in it'll completely bypass any existing aftermarket brake controller. The existing brake controller won't even 'know' there's a trailer connected. As long as the 12V feed to the 7-way connector's...
    view full answer...
  • Recommended Hayes - Proportional Trailer Brake Controller
    I recommend the Hayes - Proportional Trailer Brake Controller, # HA81742B. This has the same connection as the Hayes Time Delayed Brake Controller, # HA81760. If you have the, # HA81760 or one with the same connector, they are interchangeable. Please note the attached image.
    view full answer...
    Image 1 for
  • How Does Hayes Brake Controller install in 2012 Volvo XC60
    You will need to start with a 4-way (if you do not have one) installed on your 2012 Volvo XC60 to install a brake controller. For that you would want the # 118739 which I attached an install video for. From there you would need to convert the 4-way to a 7-way so that you can install the Hayes brake controller # HA81742B. For that you will want the Brake Controller Install Kit and 7-Way Adapter part # ETBC7. I attached installation instructions and an install video for this product as well....
    view full answer...
    Image 1 for
  • Brake Controller Installation on 1999 Ford F550 and 2000 Chevy C/K Cab and Chassis Models
    In addition to the Hayes Energize III # HA81742B brake controllers, you'll need a # HA81783-HBC wiring harness for the 1999 Ford F550. The 2000 Chevy 1 ton and cab/chassis models weren't prewired for a brake controller until the 2001 model year, so you'd need to hardwire in the controller for that vehicle. You'll also need a # HA81789-HBC universal pigtail, unless you want to cut off the black connector on the controller. I'd recommend using the pigtail, as it would allow you to easily...
    view full answer...
  • 2013 Ford Escape Brake Controller Wiring Kit Compatibility
    Since a brake controller is not a vehicle specific item, either the Tekonsha Voyager Brake Controller # 39510 and the Hayes Brake Controller # HA81742B would be compatible fit for your 2013 Ford Escape. My recommendation would be to use the Tekonsha Voyager # 39510. This is one of our better selling brake controllers and has proven itself to be user friendly and the manufacturer has a reputation for producing a high quality product. It also offers a wider range of fine tune power adjustments...
    view full answer...
  • Trailer Brake Controller Manual Override Not Functioning but Trailer Brakes Work from Brake Pedal
    Since the trailer brakes are working when you press on the brake pedal, it sounds like there could be one of two things going on here. It could be something as simple as the connections inside the controller being dirty or dusty. Give the manual override button a series of pushes and let the button snap back up into place- we just want to try to dislodge anything that might be keeping the button from making a full connection to the internal parts that operate the manual override. If the...
    view full answer...
  • Is There a Plug and Play Harness for Hayes Energize III Brake Controller on 2016 MB Sprinter 3500
    I have a solution for you, and there are some brake controllers available that can be used with a plug and play wiring harness to ease installation; however the Hayes Energize III # HA81742B is not one of those controllers and it would need to be hard wired into the vehicle no matter what. If you want to go that route you can use the # HA81789-HBC to plug into the Energize III and gives you the pigtail wiring needed to hardwire. With that said, instead of the Hayes Energize III I recommend...
    view full answer...
  • What Does Lever On Side of Hayes HA81742B Energize III Brake Controller Do
    The lever on the side of the Hayes # HA81742B Energize III brake controller is what levels the internal pendulum for the accelerometer that determines how quickly the vehicle is braking. Once installed, the lever should be pointed downward, at a 90º angle to the floor of the vehicle. This controller has a rudimentary display consisting of one LED, which isn't very user friendly. If you're pretty experienced using brake controllers, this might be a good choice for you but if you aren't,...
    view full answer...
  • BMW X5 Curt Echo Brake Controller and ETB7L 7-Way Vehicle Connector
    I would be happy to help you set up your BMW X5 for towing with a brake controller but what you have suggested will not work. You would be combining the brake and turn signals on one circuit. Basically, every time you turned on your blinker you would send power back to the brakes. I recommend adding the 7-Way RV Upgrade Kit for Trailer Brake Controller Installation - 12 Gauge Wires item # ETBC7L to your vehicle. The item # ETB7L plugs into your existing 4-way trailer connector and also...
    view full answer...
  • Wireless Brake Controller for a 2020 Ford Transit T250 w/ out a Plug in Harness
    There are no plug in adapters for the 2020 Ford Transit T250 so you will either have to tap into your van's wiring harness or use a wireless brake controller like the Curt Echo item # C51180. This Bluetooth-enabled brake controller wirelessly connects to your smartphone. The compact unit plugs in line with your 7-way trailer connector completely eliminating the bulky controller on your console and the hassle of wiring. This is a proportional brake controller that automatically adjusts your...
    view full answer...
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