Let’s say hypothetically, I hook the switch pro to one of the studs, with no lights on how quickly would it drain the battery (although I do see that it should turn itself off)
I wish I could smack whatever ram engineer decided not to power any of these fuses.
It loois like the idle current for SwitchPros is between 3-35 mA.
So assuming 40 amp-hours of usable energy in the battery, or 40,000 mAh , you’re looking at 1,600 hours worst case.
Even 35 mA is nothing to worry about. What you need to worry about is an accidentally leaving a light on, not the idle draw of the SwitchPros.
I don’t have a SwitchPros, so don’t take my word for it (refer to the manual), but it looks like you want to hook up the power module either directly to the battery or a stud, properly fused), then use the ignition input signal wire to tell it when the truck is running. That’s going to be a low current, and that’s what you need to tap into.
And yeah, that brings you right back where you started: which fuse to tap into. But remember, the SwitchPro isn’t going to draw much current from this signal wire; it just wants to know if there’s voltage on that wire. So I wouldn’t worry about tapping into F66 or whatever.
Absolutely don’t try to power your SwitchPro from a fuse tap, though; just use that for the signal.
If you already knew this, my apologies!
I use a Garmin PowerSwitch, and it works similarly: wired directly to the battery positive, with a signal wire running from a fuse tap.