trailer brakes stuck on- dodge 3500

hertfordnc wrote:
I am supposed to be getting that input from the the harness supplied by Dodge.

The other three wires in the harness do what they are supposed to;

- 12 VDC
- ground
- power to the trailer brakes.

But the wire that would serve the same function as tapping into the brake light has no voltage.

So "12 VDC" above is Black from Battery +12V,
"Ground" is White "-" from Battery,
And "Power to the trailer brakes is Blue from Controller to Trailer Connector...?

and "the wire that would serve the same function as tapping into the brake light" is the Question at Hand, and it's NOT connected to the Brake Switch as shown above...?

You say "Dodge specific." Is this Dodge new enough to be CAN/BUS with a Powertrain Control Module (PCM) and/or/maybe a Body Control Module (BCM)? I wonder if the Brake Switch tells a "Brake Light Control Module" to send a signal down the Data Bus to notify the Central Processing Unit that it's OK to tell the Output Chip to let the Brake Light Relay put the Lights on...

Could be. Our 2009 Nissan Pickup has a switch on the floorboard to keep me from cranking the starter if I don't have the clutch pushed down. OK...Switch interrupts power from Ignition Switch to Starter Relay. NO NO NO!!! The CPU is looking for a signal from that switch to come down the bus and then it directs power to the Relay. Luckily for me, a little rubber bumper had broken so the switch wasn't being pushed. I could have taped a penny over the hole the bumper left in the clutch arm. But I went high-tech and put a 1/4" capscrew through the hole with nut and lock washer.

If it's all computerized, Good Luck. Either figure it out, or I suppose you could tap into the brake lamp wiring and run THAT voltage back to the Controller Red Wire. That SHOULD work if you have separate Amber Turn Signals. If the Stop Lights are Red and they Blink as Turn Signals, really odd things are going to happen if you signal while braking.

We have enough people pulling Fivers and TT's with Dodges, somebody ought to be able to help...

Thanks for going to all the trouble of writing that detailed response.

I think my question is Dodge specific. Yes, the brake lights work.

But i am not tapped into the brake lights. I am supposed to be getting that input from the the harness supplied by Dodge.

The other three wires in the harness do what they are supposed to;

- 12 VDC
- ground
- power to the trailer brakes.

But the wire that would serve the same function as tapping into the brake light has no voltage.

Hard to help with a reference to Wire Number One but no diagram. A little like telling the bomb squad to cut the yellow wire without a camera on the bomb...

Does the Reese Wiring Diagram look about like this one?


I think there are two problems with the diagram above, but I believe we can disregard them.

1. The "40A" breaker in the upper left and the wire from it to the Trailer Connector aren't relevant to the Brakes. But the Blue Wire from the Controller TO the Connector IS relevant.

2. There should be a Ground at or to the Connector.

That said and back to the troubleshooting:

1. Engine running, you press on the Brake Pedal, lower right in the diagram. The RED wire, with the "Wire Tap (not supplied)" should go HOT with 12VDC. Is that Wire #1 in your last post? Yes it should. A Meter with its Positive probe (usually Red) from that Tap, and Meter's Negative probe (usually Black) should show "+12" on the DC Volts setting.

2. Does it?

3. Do the Brake Lights come on?

4. If 2 = No and 3 = Yes, then your Tap did NOT make connection to the wire from the Brake Pedal Switch.

5. If 2 = No and 3 = No ALSO, either

6. Brake Pedal Switch is Bad. or

7. No Power to Other Side of Brake Pedal Switch so repeat 1. EXCEPT Meter Positive goes to the other terminal of Brake Pedal Switch. Meter should show "+12" with Pedal pressed or NOT.

8. Does it?

9. Yes = Bad Switch

10. No = No Power TO the Switch. perhaps you blew a fuse tinkering with the Controller.

I'd rather use a Test Light like this



than mess with a Meter. Attach the Clip to a known good ground, then probe the +12 wiring, like at the Brake Pedal Switch, with the Ice Pick end. If there's 12V, you'll see the bulb in the pick handle light up. Pre-test the Test Light on a known good source, like the Battery, before you start so you know what to look for and what it looks like when it sees voltage.

IMPORTANT TIP: At some point you'll want to test Controller Output at the Trailer Connector. From the terminal the Blue Wire is on, to the Ground Terminal. A DIGITAL METER WILL LIE TO YOU ON THIS TEST!!! You must use a Test Light.

Please try some of this and get back to us.

So i bought a new cheap Reeese controller- and a meter and here's what I have- four wires coming form the trucks brake harness.

1- input from brake pedal
2- 12 VDC
3- ground
4- output to trailer brakes.


So, with the engine on when i press the brake pedal i should have power to wire number 1, right? It sends the signal to the controller which send power out to the trailer brake, right?

Anyway, when i press the brake i get no power to the brake signal input wire. I do have 12 VDC on the power wire and the ground is good.

Buy a new Tekonsha P2 or P3 brake controller and be done with it

Or mis wired controller

THanks, I broke out the meter and dusted off some unused brain cells. The input signal to the controller matches the input from the brake pedal but the line ot the trailer brakes remains at 12V so it's the controller.

Could be related to the emergency braking setup on the trailer...do the trailer brakes release when you unplug from the truck? If not, the breakaway kit is the likely culprit.

Break away switch defective?