Trailer Brake Controller Wiring - Installation and Setup Guide
Electric trailer brakes don’t work without a brake controller in the tow vehicle. It’s the bridge between your brake pedal and the trailer’s braking system. Without one, your camper is just dead weight pushing your truck through every stop.
How Trailer Brakes Work
When you hit the brakes, the controller sends electrical current through the blue wire to the trailer’s brake magnets. More current means more braking force. The controller regulates how much current flows based on how hard you’re braking.
Proportional vs Time-Delayed
Proportional Controllers
Use an accelerometer or motion sensor to detect how hard you’re decelerating. Apply matching braking force to the trailer instantly.
Pros: Smooth stops, less brake wear, better control in emergencies Cons: More expensive ($80-200), must be mounted level
Popular models: Tekonsha Prodigy P3, Curt Spectrum, Redarc Tow-Pro
Time-Delayed Controllers
Apply a preset amount of braking force after a configurable delay. The delay and intensity are set manually.
Pros: Cheaper ($30-80), mounting angle doesn’t matter Cons: Jerky stops, more brake wear, less responsive in emergencies
Go proportional. The $50-100 difference is worth smoother braking and less stress on your trailer’s brakes.
Wiring Connections
A brake controller has four wires:
| Wire | Color | Connects To |
|---|---|---|
| Power | Red | 12V ignition-switched source |
| Ground | White/Black | Vehicle chassis ground |
| Brake Switch | White | Brake light switch wire |
| Output | Blue | 7-pin connector pin 5 |
Power Wire
Connect to a 12V source that turns on with the ignition. Use the fuse box — find an ignition-switched slot and add an inline fuse (15-20A).
Ground Wire
Bolt to bare metal on the vehicle chassis. Scrape paint off the contact point and use a star washer. Bad grounds cause weak or intermittent braking.
Brake Switch Wire
Tap into the wire at the brake light switch on the brake pedal. This tells the controller when you’re pressing the brake. Use a T-tap connector or solder the connection.
Output Wire
Runs to the blue wire at the 7-pin connector. This is the signal wire to the trailer brakes. Install a 20-30A inline circuit breaker on this wire for protection.
Gain Settings
The gain knob controls maximum braking force. Too low and the trailer pushes the truck. Too high and trailer tires lock up.
Setting gain correctly:
- Find a flat, empty road
- Drive 25 mph
- Apply brakes firmly (not emergency stop)
- Adjust gain until the trailer brakes engage smoothly without locking wheels
- You should feel the trailer helping slow down without jerking
Re-adjust gain when towing different weight loads. A fully loaded camper needs higher gain than an empty one.
Installation Steps
- Mount the controller under the dash within reach of the driver
- Proportional controllers must be mounted level — use the built-in leveling indicator
- Run the power wire to the fuse box with an inline fuse
- Connect ground to chassis metal
- Tap into the brake light switch wire
- Run the output wire to the 7-pin connector’s blue wire
- Test with the trailer connected — press the manual override and check that trailer brakes engage
Troubleshooting
No trailer brakes at all: Check the blue wire connection at the 7-pin plug. Then check ground connections on both truck and trailer. A bad ground is the #1 cause of brake failure.
Brakes grab too hard: Turn the gain down. Also check that the brake magnets aren’t worn — worn magnets create uneven braking.
Brakes only work intermittently: Corroded 7-pin connector. Clean the contacts and apply dielectric grease.
Controller shows “no trailer” error: The controller can’t detect a load on the output wire. Check the blue wire continuity from controller to 7-pin plug and from 7-pin plug through to the trailer’s brake magnets.
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