Hard Wired Radar Detecor
Wouldn't it have been easier to run a wire from the IGN port in the fuse panel up the A-pillar to the radar detector? Then the detector would go on and off with the ignition (who needs it when your not driving?) and you wouldn't be hacking wires from other circuits. The IGN, BATT and ACCY ports in the fuse box are 15-amp circuits designed by GM for adding aftermarket accessories.
Yes - Wiring it to the IGN or BATT port would be preferred and recommended.
Since I am using the cigar lighter as a switch, tapping in to that circuit was easier at the time. I've never forgotten to turn off the detector; however my wife did once and drained the battery. (So now we have to have post-drive inspections...) Considering that grief, it WOULD have been less work overall to tap in to the IGN circuit!
