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Universal Part
UPC: 612314511402

TriFlex Proportional Trailer Brake Controller #51140

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  • Triple-axis, motion-sensing accelerometer for highly responsive, smooth stops
  • Third axis provides dynamic power adjustments when going up or down a hill
  • Nine levels of sensitivity adjustment for varying loads or driving conditions
  • User-selectable power output and trailer brake light activation
  • Automatic leveling and calibration eliminate setup requirements
  • Digital display shows power adjustments in 0.1 increments
  • Built-in reverse-polarity and short-circuit protection
  • Tow vehicle 'low voltage' and trailer disconnect indicators
  • Compatible with low-volt, PWM, ABS, cruise control and electric over hydraulic
  • Mounts at various angles, above or below the dash, to increase usability
  • Auto sleep mode prevents battery drain after five minutes of idle time
  • Plug-and-play install with vehicle-specific quick plug harness (sold separately)
  • Limited lifetime warranty


  • Includes mounting hardware

Guides & Install Sheets

Product Videos

  • Product Videos CURT Brake Controls Introduction
  • Product Videos CURT TriFlex Video Users Guide
  • Product Videos The CURT TriFlex Brake Control


  • Part TypeBrake Control Unit
  • HUB_USAD25
  • Shipping Weight0.550
  • MaterialBlank
  • Axles1-4
  • ActivationInertia accelerometer
  • Mount AnglesVarious
  • Level AdjustAuto
  • WarrantyLimited Lifetime

WARNING: Cancer and Reproductive Harm -

The TriFlex™ proportion-based brake controller features a compact size, a digital display and the ability to manage up to eight brakes at a time. The feature that sets the TriFlex™ apart from many others is its triple-axis motion-sensing accelerometer. This integrated circuit component allows the TriFlex™ to detect every motion of your vehicle and trailer with exact precision and to then apply the perfect amount of braking power for every situation. The TriFlex™ also automatically adjusts brake output when going up or down a hill and is compatible with anti-lock brakes and cruise control. It comes with a mounting bracket and hardware and can be mounted at various angles on your vehicle's dash. Best of all, like other CURT brake controls, the TriFlex™ is protected by a limited lifetime warranty.

This CURT trailer brake controller is designed to work with quick plugs so it can readily plug into your vehicle's original equipment socket. It also includes a mounting bracket and hardware for easy installation. A brake controller should be mounted somewhere on the dash of your vehicle, and we recommend putting it below the steering wheel, either on the right or left side of the steering column. This way the control will not block your view when driving, but it will remain accessible and visible when adjustment is needed.

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  1. 60%


    There is SUPPOSED to be voltage on the blue wire when idle.

    Good Product. I talked to tech about the voltage on the output blue wire when sitting idle. He says that is normal for the Triflex. It is looking for the trailer by shooting " dead voltage" down the blue wire. He said he gets calls about the voltage output all the time. For guys like me that have installed brake controllers for a little while, this "dead voltage" reading would tell us that the trailer is not moving with the voltage applied on the output.
    Thus the controller must be defective.. We are used to a blue wire not showing any voltage until the brake or the override is applied.
    I'm thinking that if you want to cut down on phone calls and the confusion that the idle voltage is obviously causing your consumers that you PUT A NOTE IN THE INSTRUCTION MANUAL REGARDING THE " DEAD VOLTAGE " output - Please!
    Not for me, I learned my lesson - but for the rest of us old school installers they may find that information helpful.

  2. 100%


    easy to install and use

    explanation that comes with the unit are easy to understand and follow. I had to buy an extra quick plug wiring because the one installed on my vehicle was a flat 4 connector type. Other than that, everything went fine.

  3. 100%


    Triflex brake controller

    I bought this item because of the reputation of Curt products and I was not disappointed. Easy to follow installation and set up also bought the extension harness for clean looking install. Highly recommend this product.

  4. 40%


    Triflex Controller sleep mode did not work

    We purchased the brake controller December 20, 2017. Drove to California with trailer in tow behind our 2014 Nissan Frontier. All worked really well.
    May 2018, we left the Frontier for two days, tried to start it and the battery was dead; unusual for a 3 year old factory battery. Oh well, we went to Costco, purchased a new Interstate, and travelled a lot more until November 29. We left the truck in a heated garage for 12 days and found the battery was dead again!. We charged the battery; it kept running lower and lower. We unhooked the battery from the truck, and the charge stayed at 95% for over 18 hours. So... Today, after having our mechanic look over the situation, it turns out the Brake Controller was pulling 75- 80 amps instead of "sleeping".
    We are going to talk to our RV repair place and let them know the situation. Hopefully, they will replace the brake control without charge. Heck, we're already out the cost of a battery and one hour of mechanic's time.

  5. 100%


    Triflex brake controller won't give full braking power to the trailer brakes.

    The brake controller won't give full power to the trailer brakes when I need them the most. I have never been able to get it to give the max power under any braking situation. It seems like it works off of G-force or a inertia switch. but it won't help me stop hard enough to create the g-force it needs to apply full power. The old style use to ramp up to the max power you set it for regardless of G-force. I prefer the old style much better.

  6. 40%


    It won't give full braking power when I need it most.

    The controller seems to work off of G-force or inertia. when I need to brake hard especially in the rain it won't give full power to the trailer brakes and the trailer pushes my truck. The old style brake controllers used to ramp up to full power or whatever you set it to regardless of the G-force.

  7. 100%


    Great controller and customer service

    I've been using the TriFlex controller for over 4 years without a problem. I recently experienced a problem with the sensitivity slider adjustment on the controller. Without hesitation, Curt customer service offered to send me a replacement unit along with a postage paid label to return my current controller. That was totally unexpected and further strengthens my opinion of an already great product.

  8. 100%


    51140 Brake Cont. Cust Svc

    I was very impressed with the customer service I was given by Mike at the technical support 800#. I was connected to a live person within a minute of calling and Mike was very helpful and knowledgeable about the 51140 brake controller we had installed in our vehicle. Also, the solution he gave me worked and I was able to get our unit working again after an error message had caused it to stop working. The fix was quick and easy. Very nice customer support!!

  9. 100%


    51140 Brake Controller

    I highly recommend Curt trailer brake controllers as I had an issue with my original 51140 controller becoming defective after about a year in service - I called customer support and was immediately sent out another controller no charge and it was delivered to my door within 5 days - This is what I call a company that stands behind it's products! It's actually quite refreshing to deal with a company like Curt because all to often you have to fight with a company to get a product repaired and or replaced. Well done Curt!
    I will make sure I let others know about these brake controllers and my experience with their customer service - they are truly second to none!

    Thanks again

    Mike Wazonek
    Owen Sound, Ontario, Canada

  10. 100%


    Nice compact unit

    I have never seen a brake control that is so small and easy to use. CURT is the best!

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