Testing Vehicle 7-Way for 12V Power Signal for Charging Breakaway Battery

Question:

Is the charging light supposed to be on when the 7 way is plugged in but the truck ignition switch is off

asked by: Bruce N

Expert Reply:

Some vehicle's 7-way will have a 12V power circuit that remains active at all times (even with the key off) while others will have this circuit off unless the key is in the accessory position or the engine is running. This is not consistent between auto makers nor vehicle models. If an aftermarket 7-way was added to a vehicle it could have been set up either way.

If you have a circuit tester like # PTW2992 you can test your specific vehicle to see under what conditions that 12V auxiliary power circuit is active. The video linked shows an example of using a tester like this.

Ground the tester to the 7-way ground contact (7:00 position) and then apply the probe to the 12V pin (1:00 position) as shown in the photo. If you detect no power try turning the key to the accessory position and test again; then try starting the engine and test again.

Your breakaway system like Hopkins Engager # 20400 should show power to one of its LED indicator lights when you press the test button. If you have power at the vehicle socket but not to the breakaway kit then you will need to check the trailer wiring for damaged wires, a short or a corroded trailer plug.

expert reply by: Adam R