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 use an FZ-1 Fuzeblock for all my accessories. A few are "always on", others are switched. Yeah, it's extra money, but every accessory is separately fused, easily connected, and the wiring becomes greatly simplified.