Why are trailer brakes always ON? - I have been checking my trailer plug pins to determine the normal activation voltages. One thing that is very puzzling is that the ...

I have been checking my trailer plug pins to determine the normal activation voltages. One thing that is very puzzling is that the lower right spade (Elec Trailer Brakes) is always hot. eg. 12v.

Shouldn't this just come one when the truck brake is activated?

have you checked to make sure the wire to that spade is blue? you can disasemble the trailer plug on the truck to make sure or correct it.
people have been known to match the truck to their trailer because they couldn't wire the trailer correctly to begin with.

Haven't analyzed the factory wiring yet. It's a brand new truck. Everything works on my covered trailer. But on the open trailer the running lights don't go on. So I checked the pin-out and the blue trailer brakes pin is ALWAYS hot (12v).... Weird.

do you have a brake controller/ sounds like it may be shorted out. your right tho the blue wire is electric brakes and should only come on with the truck brakes applied.

well just for reference here is how my truck is wired.

as your looking at the rear of the truck. theres a notch/cutout on topend of the truck connector.

brown -running lights-top left
red -12v hot-top right
white- ground return- bottom left
yellow-left turn-left side
dark green-right turn-right side
green-backup lights-center
blue-electric brakes-bottom right
and the light blue wire thats hanging off to the right side by itself is for clearance/third brake lights

Thanks... yes, that's the same pin functions that I have. And, also, I have the factory-installed brake controller.

Here's the rest of the story... I was pulling my trailer over the mountains between Calif and Oregon. I noticed my trailer lights were all out. I found that the "Trailer Brake" fuse was burnt out on my truck. Replaced it and all of the lights came back on.

So, now as I research further, I see that my "trailer brake" connection ALWAYS has 12 volts to it. And it's interesting to know that if you're trailer brakes blow a fuse, that it takes ALL OF THE TRAILER lights with it.

hmmm interesting... sorry if this is a silly question but do you have brakes on your trailer?

No, that's actually a good question. I haven't used the trailer since I got home but it "seemed" to be working okay once I replaced the fuse in the middle of the mountains. I never had a need to give it a real test after that.

And - last week i took a small 12v dry cell and touched it to the trailer brake pin on the trailer connector... you could hear the activators working at the wheel hubs. So my conclusion then, was that the brakes were working okay.

I know little on electric trailer as I never used them, but just a thought would the trailer brakes be energized when the truck is in park as to help hold the rig while not in motion? Check to see if you still have voltage when the truck is in drive. On the blown fuse manufacturers combine vital circuits with lights in an effort to help draw attention to blown fuses.

Without researching the wiring diagrams, this is a total guess. Could it be that it is hot in order to charge the breakaway brake battery on the trailer?

no the aux power is used to charge the brake away battery. the electric brakes are not powered in park.