'07 SD - is there a wire in the harness to accomodate a backup warning device? I found a sounder that works on 12 or 24V DC but unsure about the current pull. I have a feeling it would draw too much current to tap into the standard reverse light.

 

If you are worried about your factory wiring, install an inline fuse holder before the backup alarm. Try a 10 amp fuse, I suspect you will be fine.

If your backup alarm draws more than that, use a relay, coil to backup lights and ground, output from trailer charge circuit to backup alarm.

 

You could use the Trailer reverse circuit that way if it dose blow a fuse you will not loose the trucks rev. lights seeing how most trailers do not come equiped with rev. lights.