How to Wire 12V Auxiliary Power Circuit in 7-Way RV Wiring

Updated 04/03/2018 | Published 04/01/2018

Products Featured in This Question

Adapter 4 Pole to 7 Pole and 4 Pole w/Test Lamps

(312)

$42.73

10 Gauge Wire - Blue Primary - Per Foot

(104)

$1.74

Ring Terminal - 12-10 Gauge Wire - 3/16" Ring ID

(69)

$1.33

Pollak Circuit Breaker - Cycling/Automatic Reset - 40 Amp - Straight Mount Bracket

(49)

$7.40

Question:

Have the Adapter 4 Pole to 7 Pole and 4 Pole w/Test Lamps Item # C57674 hooked up as your video explains for a 2015 Subaru Outback. I have a small tear trailer I built and would like to provide power to charge the battery while towing. Would you happen to know where I would pull power from to supply 12v through the 7 pin connector to use for charging the 12v trailer battery while towing?

asked by: Troy B

Expert Reply:

On standard 7-way RV-type trailer wiring the contact at the 1:00 position as you view the socket carries the 12V auxiliary power circuit that can be used to maintain a trailer-mounted battery as you travel. Please refer to the linked photo.

Note that this charge is enough to maintain a charged battery while you drive but it does not deliver enough power to re-charge a depleted battery. For re-charging a depleted trailer battery you really need a shore-power AC charger like the NOCO # 329-GEN1 which works to charge lead acid batteries up to a 230-amp-hour rating.

On the Curt 4 Pole to 7 Pole Adapter # C57674 this contact is fed by the black pigtail lead. This wire should connect to the battery + terminal through a 40-amp auto-reset circuit breaker like # PK54540 using 10-gauge wire like # 10-1-1 and ring terminals like # 44-5310A.

I have attached diagrams of the 7-way plug wiring pin out.