4-Pin vs 7-Pin Trailer Wiring (Canada)
Trailer wiring
Four-way and seven-way plugs are not interchangeable fashion choices. Four-way covers basic lights. Seven-way adds electric brakes and usually a charge line. Pick the plug that matches the trailer circuits you actually use, then wire the vehicle to support them.
We stock CURT adapters and harnesses for both plug styles, with free shipping anywhere in Canada.
Deeper wiring?
Wiring harness guide.
Brakes?
Do I need a brake controller.
Hub:
towing guides.
What each plug carries
| Plug | Typical circuits | Best for |
|---|---|---|
| Four-way flat | Running lights, brake lights, left and right turn | Light utility trailers and racks that only need lamps |
| Seven-way blade | Lights plus electric brakes, twelve-volt charge, often reverse | Electric-brake trailers and RV-style connectors |
If the trailer coupler area has a seven-way plug and electric brake magnets, plan a brake controller in the tow vehicle. A four-way-only vehicle cannot modulate those brakes through a light-only adapter.
When an adapter is fair
Adapters are fair when both sides already have the circuits you need and you only need to change the connector shape. Examples: vehicle has four-way lights and the trailer presents a seven-way shell but you are only running lamps, or the vehicle has seven-way and the trailer is a simple four-flat. Adapters are the wrong answer when you need brake output that does not exist yet.
Adapters we commonly sell
CURT part 57184Four-flat to seven-wayLight-circuit mapping from a four-flat vehicle to a seven-way trailer plug.$40.27 CAD
CURT part 57185Four-flat to seven-way with bracketSame job with a bracket so the adapter has a home on the bumper.$49.67 CAD
CURT part 57240Seven-way to four-flatWhen the vehicle already has seven-way and the trailer is four-flat.$18.10 CAD
CURT part 57672Four-flat comboFour-flat to four-flat and seven-way. Confirm on the product page.$52.51 CAD
CURT part 57102Seven-way and four-wayCommon seven-way to four-way adapter. Confirm genders on the product page.$75.07 CAD
Official CURT plug context
How to Select a Trailer Hitch
Useful class context when the hitch and wiring are chosen together.
Watch on YouTube
