How to Wire 12V Power to Prevent Trailer From Draining Tow Vehicle Battery When Vehicle is Shut Off

Question:

How would I wire the 12V+ feed to my trailer connector so its not live when the ignition is shut off? Im afraid of a draw from the trailer draining my trucks battery if I forget to unplug the trailer overnight.

asked by: Abe W

Expert Reply:

To prevent your trailer 12V accessories (and/or battery) from draining your tow vehicle battery when the vehicle is shut off you need the Battery Isolation Solenoid # PK5231201. This basically allows 12V power to pass through but then is also wired to the ignition of your vehicle. When you shut the vehicle off this isolation solenoid cuts the power from your vehicle battery so you don't have to think about switching anything manually.

If you just need the charge line for your 7-Way then that would include 10 Gauge Wire # 10-1-1 and a 40 Amp Circuit Breaker # 9510. If you don't have anything for your vehicle 7-Way then you'll need an appropriate 4-Way connector and the Universal Wiring Kit # ETBC7 along with the isolation solenoid I mentioned above.

Attached is a wiring diagram for the ETBC7 kit. The only thing not pictured is the isolation solenoid. This will be placed closer to your tow vehicle battery which you can see in the linked video.

expert reply by: Jon G