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Constant Voltage on 12V and Brake Controller Output Wire with Curt TriFlex Trailer Brake Controller


I have a Curt 51140 Brake Controller and a Curt 51515 harness installed in my 2014 Toyota Sienna. I plug a tester identical to the pollak PK12741 into my 7 pin socket and the 12v and bk lights both light up with the van ignition off and no brakes applied. I grab my volt meter and the 12v pin 1oclock position measures 12.2 volts. The 5 oclock pin trailer brakes measure 11.2 volts. I read in some of your other answered questions that a small amount of voltage is normal. 11.2 volts doesnt seem small to me. I cut the blue wire from controller plug harness 51515 and the 11.2 volts ped to 0. I thought for sure that my controller was faulty. I called Curt tech support and explained my findings in hope that they would honor the lifetime warranty. They told me that the 11.2 volts was normal, and I shouldnt worry. He further went on to say that the amperage is what matters, not the voltage at the plug. He lost me at that point, amperage isnt my thing. Can you please clarify this? I have to drive 100 miles to pick up my trailer, and dont want to have locked up brakes when I get there.


Expert Reply:

When testing the wire functions after installing the Curt TriFlex Trailer Brake Controller # C51140 and Wiring Harness # C51515 in your 2014 Toyota Sienna, it is normal for both the 12V and brake lights on a tester like # TR20117 to light up without actually activating the brakes. This is because the brake controller sends out a small trace current to look for a completed circuit. I have attached a demonstration video on a similar 7 Way Trailer Connector Vehicle Tester # TR20117 that shows this right around the 1:10 mark.

The 12.2 and 11.2 volts you measured with your meter are normal and Curt calls this "dead voltage", which you can look at as more of a false reading because of how the Curt brake controllers work. When they told you that amperage is what matters here, they are referring to when the wires actually draw a current. An actual load is only going to be placed on the current when you press down on the brake pedal or use the manual override switch on the controller. This is what they are referring to when they talk about amperage as opposed to the small voltage that is constantly being shown on the tester or meter that you used.

expert reply by:
Chris R

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