Brake Controller/Brake Issues.

[SMarquez]

Long post but I'm trying to figure out which problem came first.

After a trip in March right before the shutdown, I traveled to Paso Robles during which time it was raining. I had trouble with my truck, lost cruise control, brake lights and trailer braking. The braking wasn't a big deal which is a testament to using enough truck.
So I get home and check the trailer brakes and find the front drivers side brake wire broken so I know that brake couldn't have been working. I reconnect everything and adjust the brakes and test. I have no brakes on the right side. After much messing around I decide the magnets are shot. No actuating after powering them direct with a battery. I decided to get the electrical in the truck squared away before I chase this around.
So I get the truck fixed and decide to test the brake controller. It turns out I have 12.5v at the blue wire right out of the controller which I thought only got powered when it was actuated. I only have 4.5v though the brake wires. I know the controller kind of acts like a rheostat for the brakes but shouldn't I see 12v when I hit the slider? I'm a little confused. Any help out there?
Thanks

[dedmiston]

That's a weird one. I'm glad you got it fixed.

[SMarquez]

Here's the follow-up.
I took the truck to a auto repair shop I trust. They had it for a week and decided it was the brake pedal switch though I had already replaced it. Their non-OE switches didn't work. This became a real head scratcher. They then opened up the switch and said it looked defective, aligned some contacts and that fixed it. Remember, the ABS problem started with the replacement switch. I probably should have just gone straight to the dealer for an OE switch.

[Dirtclods]

I've have a two different issues with trailer brakes. One was at the connecting it was rusted inside of the female connector. The other was at the brake it self on one side one of the wires ripped out.

[Nv_Guy]

While there may be voltage, there may not be any amperage,so check it with an old school test light to see if the test light bulb lights. Some controllers output a sense voltage (with virtually no amp output) to "look" for shorts & verify continuity, so that might be what you are seeing. Also, some controllers need to be connected to a load before they will deliver an output.

[mapguy]

couple important pieces of info are missing:

Truck make/model
Brake Control make/model

[opnspaces]

Well that's a bit weird then. If you used a factory harness and it was working all this time then it should be working unless something shorted. You might want to poke your head under the dash and see if the wires to the controller are still hooked up correctly. My WAG (Wild A-- Guess) is that the brake light switch is still a problem.

Find the wiring diagram for your brake controller and make sure that the wires are getting the correct voltages.

For a Prodigy it's

BLACK wire 12V positive.

RED This is the brake switch wire. It should read 0 until you press the brake pedal.


WHITE wire is ground.

BLUE wire is the brake signal. This is typically the 5-o-clock position if you look into the socket on the back of the truck.

From what you are describing I'm betting you are getting 12 volts from the brake pedal when you are not touching it.

[SMarquez]

I was so frustrated when I posted this I left some info out.
The controller went on the truck a long time ago, a factory pigtail wired into the controller. The brake pedal switch was replaced by me. I forgot to mention that when I replaced the switch it triggered an ABS light. At that point I got a B1485 ABS code that said brake pedal position circuit short to battery. The guy that did the repair said he replaced the switch but it didn't fix the problem. He thought that there was a problem with the switches from his supplier. He opened my original switch and said the contacts were out of alignment. He tweaked the contacts and that fixed it. The ABS light went out and I got the cruise control back. It makes me think that there is a problem with the controller. I do trust this guys shop and have had work done before BUT, he is not a dedicated auto electric shop. I'm think I should buy a genuine Ford BP switch and see where it goes from there.

[opnspaces]

You are correct you should not be getting 12v at the brake wire when disconnected. My guess is something was hooked up incorrectly when the truck was worked on. which brings up two questions.

What was the fix on the truck? Was the turn signal or brakelight switch replaced?

Is your brake controller using a manufactured cable to connect to the truck wiring? Or is it just scotchlocked onto existing under dash wiring?

I'm thinking the guy that did the repairs probably hooked the blue wire up to the wrong side of the brake light switch.