How to Make the 12 Volt Power Circuit of a 7-Way Only Active When Vehicle is On

Question:

I will be installing a Tekonsha brake controller, the universal brake controller kit and 7 pin wiring harness to my car for electric brakes. Id also like to use the 2 12V pins in the 7pin connector to power my 12V fridge and to charge my battery while under way. Rather than power these 2 lines directly from the battery via a fuse or CB, Id like to add switched relays to these terminals so they are only operational while the vehicle is running. Can you recommend a set of universal relays with inline fuses or a wiring kit for this purpose? Thanks etrailer!

asked by: Mark J

Expert Reply:

I believe I can help. The # ETBC7 comes with everything needed to install the # 90885 brake controller plus a fully functional 7-way. But to make it so that the 12 volt accessory circuit of the 7-way is only active when the vehicle is on you will also need to install an isolator solenoid as well on the 12 volt circuit. For that you would need the # PK5231201. See the picture I attached to see how it will wire in.

Basically the center pin will need to get run to a keyed power source since it is what completes the circuit and the other two pins will install inline with the 12 volt power circuit.

You should note that this circuit can't really charge a trailer battery very well. At best it can help maintain a charged trailer battery. You also would want to run your fridge off of the battery instead of this circuit to prevent overdrawing this circuit.

I attached an install video and instructions for the # ETBC7 for you to check out as well.