Where Connect 7-pin power lead

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May 24, 2005
Bonsall, California
I got Ailiner travel trailer. I don't need to connect up the trailer breaks but I do need extend my current flat four pin trailer connector to a 7-pin to charge the trailers battery. I know I need take an extra connection from a "fused battery lead" but I ask where can I do this from the raed wiring harness. Maybe the red lead that runs with the black lighs lead? or must I wire directly from the LC's battery?
must I wire directly from the LC's battery?

Yes. Use _at least_ a 12AWG wire, preferably much larger, plus a self resetting RV type 30 amp circuit breaker up front near the main battery.

Picking up 12 volt power in back is a very BAD idea - the wire size is way too small, with too much voltage drop - the trailer's house battery would never get a full charge and you risk blowing that circuit's fuse when the house battery is really low and the charging current is high.

Run a dedicated large wire and never worry again. I personally would run a 12 AWG blue wire up to the dash area, leaving a couple of feet extra, just in case you want to add a brake controller in the future. The cost and time is minimal if you do this while running the battery charge wire.

BTW, NAPA sells stranded wire by the foot, so you don't have to buy either a dinky roll that is probably too short, or an excessively large spool. 30 feet should be plenty for the battery charge wire.

PS: I ran my wires along the left side of the cabin, behind the rear quarter panel and under the door sill trim. Pretty easy.

Make sure your trailer's ground circuit is in top condition, with a separate wire going through your seven pin connector to chassis ground. Don't rely on the ball to coupler interface for a return current path.

John Davies
Spokane WA USA
Last edited:
Thanks. And so good an answer let's close this thread.

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