Trailer Brake Controllers
How to Install a Trailer Brake Controller
Four wires, one harness, one mounting decision. Most of the difficulty is choosing the right parts before you start.
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Short answer
A hardwired controller needs four connections: battery positive through a fuse, ground, the brake switch signal, and the output to the 7-way's brake pin. A vehicle-specific harness supplies all four without cutting anything.
The four circuits
| Circuit | Typical color | Function |
|---|---|---|
| Battery + | Black | Fused feed that powers the trailer brake magnets |
| Ground | White | Return path - a clean chassis ground, not a paint-covered bolt |
| Brake switch | Red | Tells the controller the pedal has been pressed |
| Brake output | Blue | Goes to the 7-way's brake pin and out to the trailer |
Colors follow the common convention; confirm against your controller's own instructions.
The sequence
Installation
Buy the right harness
A vehicle-specific harness plugs into an existing connector, usually under the dash on vehicles pre-wired for towing. Matching year, model and trim is the whole job.
Choose the mounting position
Within reach of your right hand and in your field of view, without blocking a vent, a knee or a panel you need to remove. Test-fit before drilling anything.
Connect the harness
Plug into the factory connector. If your vehicle is not pre-wired, each of the four circuits is connected individually - and the battery feed must be fused at the battery end.
Mount the controller
Current units self-level, so angle is not critical. Older pendulum designs required a level mount within a narrow range.
Reconnect the battery and power up
The controller should indicate power with no trailer connected, and indicate a connection when one is plugged in.
Test with the trailer attached
Plug in the trailer. The controller should detect it. Apply the manual override with the vehicle stationary and have someone confirm the trailer brakes engage.
Set the gain
In an empty parking lot at about 25 mph, apply the manual override alone and raise the gain until the trailer brakes firmly without locking.
Quick picks
Tap any row to jump to the full write-up. How these are chosen - and what we do and do not claim to know - is published in full on our research methodology page.
| # | Product | Best for | Our read | Price |
|---|---|---|---|---|
| 1 |  Tekonsha Primus IQ Trailer Brake Controller Straightforward install | One truck, one trailer | Compact, fits where bigger units will not | Check price on Amazon #ad Affiliate link - we publish no price; Amazon shows the current one |
| 2 |  REDARC Tow-Pro Elite Electric Brake Controller Cleanest result | Clean dash installs and off-road towing | Knob in a switch blank, box hidden | Check price on Amazon #ad Affiliate link - we publish no price; Amazon shows the current one |
| 3 |  CURT Echo Mobile Trailer Brake Controller No install at all | Rental trucks and borrowed tow vehicles | Plugs into the 7-way | Check price on Amazon #ad Affiliate link - we publish no price; Amazon shows the current one |
1. Straightforward install
Tekonsha Primus IQ Trailer Brake Controller
Tekonsha · Best for one truck, one trailer
Proportional braking without the memory, the boost profiles or the big display. For one truck and one trailer, that subtraction costs you almost nothing in how the rig actually stops, which is why it stays the default recommendation for a first controller.
We have not sourced a full specification table for this model from the manufacturer’s own site at a stable address. Rather than repeat figures we cannot cite, the assessment above is limited to what the design and the maker’s published description genuinely establish.
What works
- Proportional response at a far lower price than a flagship controller
- Small enough to mount where a larger unit will not fit
- Mounts at a range of angles without needing to be level
What does not
- No per-trailer memory, so a second trailer means re-setting gain each time
- Display tells you much less when something is wrong
Skip it if
Not the one if you swap between a light utility trailer and a heavy camper - without stored settings you will eventually drive off on the wrong gain.
#ad Affiliate link - we publish no price; Amazon shows the current one
2. Cleanest result
REDARC Tow-Pro Elite Electric Brake Controller
REDARC · Best for clean dash installs and off-road towing
The control head is a single knob you can mount flush in a blank switch panel, with the electronics hidden elsewhere. It switches between proportional and user-controlled modes, which matters on loose surfaces where proportional braking reads the wrong thing.
We have not sourced a full specification table for this model from the manufacturer’s own site at a stable address. Rather than repeat figures we cannot cite, the assessment above is limited to what the design and the maker’s published description genuinely establish.
What works
- Remote knob mounts into a factory switch blank instead of hanging under the dash
- User-controlled mode gives constant output where proportional sensing misreads the surface
- Electronics sit out of sight and out of the way of knees
What does not
- Two-part installation is more work than a single-box controller
- No numeric display of what it is doing
Skip it if
Not worth the extra install work if you only ever tow on sealed roads and do not care how the controller looks.
#ad Affiliate link - we publish no price; Amazon shows the current one
3. No install at all
CURT Echo Mobile Trailer Brake Controller
CURT · Best for rental trucks and borrowed tow vehicles
Plugs into the 7-way instead of being wired under the dash, and runs from a phone app over Bluetooth. Tri-axis inertia sensing means it does not care how it sits. The trade is that your brake interface is a phone, which is a real objection and not a small one.
Published specifications
What works
- No wiring, no drilling, and it moves between vehicles in seconds
- Tri-axis sensing removes the level-mounting requirement entirely
- Ideal when the tow vehicle is not yours to modify
What does not
- The manual override lives in a phone app, which is the wrong place for it in an emergency
- Rated for one and two-axle trailers only
Skip it if
Not for a triple-axle trailer, and not for anyone who wants a physical lever they can hit without looking.
#ad Affiliate link - we publish no price; Amazon shows the current one
Raw specifications: CURT’s own page. We earn nothing on that link.
Common installation mistakes
- Grounding to a painted surface. Paint is an insulator. Scrape to bare metal or use a factory ground point.
- No fuse on the battery feed. The feed carries real current to the trailer magnets. It must be fused at the battery.
- Mounting where you cannot reach the override. The manual lever is the whole point of a hardwired unit.
- Skipping the gain procedure. An installed controller on a default setting is a controller that is not doing its job.
Key takeaways
- Four circuits: fused battery feed, ground, brake switch, brake output.
- A vehicle-specific harness avoids cutting anything.
- Mount within reach of the manual override.
- The install is not finished until the gain is set on the road.
How we sourced this
Every figure on this page came from one of the following, each fetched while the page was written. Where a manufacturer or regulator does not publish a number, we say so rather than estimate it.
Common questions
- Does my vehicle have a tow prep connector?
- Many vehicles sold with or prepared for a tow package do, usually under the dash near the steering column. The harness manufacturer's fit guide will tell you whether yours is covered.
- Can I install one without a harness?
- Yes - each circuit can be connected individually. It takes longer, requires identifying the brake switch wire correctly, and the battery feed must be properly fused.
- How do I know it is working?
- With the trailer connected and the vehicle stationary, apply the manual override and have someone confirm the trailer brakes engage. Then set the gain on the road.
More in Trailer Brake Controllers
If the trailer has electric brakes, something has to tell them how hard to work. That something is a controller, and how you set it decides how the rig stops.
Read next
How to
Adjusting Brake Gain
The empirical gain procedure, how to read under- and over-braking, and the loads that make a reset necessary.
Reference
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The brake circuit from battery to magnet, the role of each conductor, and the connection points that cause most faults.
Best brake controller
Best Brake Controllers
Hardwired and plug-in proportional controllers compared on published specifications and how each behaves when something goes wrong.
Troubleshooting
Trailer Brakes Not Working
An ordered diagnostic sequence for electric trailer brakes, from the connector outward, with the checks that need no tools.
Found something out of date, or a figure you can source better than we did? Corrections get read first. How we research explains how these pages are put together, and contact is one click away.