Quote Originally Posted by druggr View Post
You'll have to install a relay. The seat gets wired to the secondary side of a relay. The primary side of the relay is then wired to "keyed power." Keyed power means that the relay is turned on once the ignition switch is turned to the "on" position. Once the relay is tuned on, it then supplies power to the seat's control switch. For the seat to work, the ignition has to be on, and the seat's control switch must be on.

Often aftermarket seats provide more heat then OEM ones.

If you need to know how relays work, go here. I believe they call the primary side the "input" and the secondary side the "output."

http://www.explainthatstuff.com/howrelayswork.html
I wired my auxiliary electrical toys through an auxiliary fuse panel that is switched by a relay controlled by the Engine Oil Pressure switch. The bike (and alternator) has to be running (not just the ignition switch on) to power these heavy draw items so they don't draw directly from the battery. This is a little extra insurance to prevent a drained battery.