Trickle charger does not work

[TandM]

I installed an RVI trickle charger in my toad to maintain the battery while flat towing. I have an RVI3 brake system installed as well. I was planning on hooking the trickle charger to the brake monitoring pin or the auxiliary power pin at the seven pin harness at the motorhome. However neither pin shows 12V when combined with the ground pin on the harness. I am using the other pins on the harness to control the brakes, turn signals, and lights on the toad.

Any ideas why the brake monitoring pin for the auxiliary pin is not providing a charge?

planning on towing 2009 Subaru Forester

[TitanMike]

Blown fuse? Blown fusible link? Bad relay? Aux power line not connected to coach charging system/battery?

I'd start at fuse panel and look for a fuse for this circuit that's either blown or not installed.