How to Determine the Amperage on the 12 Volt Power Circuit in a Trailer Connector

Updated 11/14/2013 | Published 11/12/2013

Question:

I have a 7 blade connector on my truck and was wondering what the power output would be going back to the trailer. I understand its 12 volts but what is the amperage?

asked by: Sean

Helpful Expert Reply:

The amperage on the 12 volt power circuit will depend on the amperage draw of the item receiving the power on the trailer. When aftermarket 7-way trailer connectors are installed on vehicles, it is recommended to have a 40-amp circuit breaker inline on the power wire going from the trailer connector to the battery.

If your truck has factory trailer wiring, there will be a fuse in the fuse box designated for that circuit. You can check your owners manual to see the names and locations of the fuses. The fuse would have a label similar to Trailer Tow Battery Charge or TT Battery Charge. Most vehicle manufacturers use a 30 amp fuse, but I recommend verifying the fuse in your truck if amperage draw is a concern.

expert reply by: John H