2000 Blazer LT heated leather seat

My 2000 Blazer with heated leather seats has a problem. The passenger seat heat stays on all the the time and drains the battery. Had to pull the fuse to shut it off. It even stay on when the switch is off. Pretty good at fixing things. Anybody have an idea what controls the seat heat? I would like to fix it myself.
MADDMANN

Isn't there a switch for it on the seat?

Might want to start there.

Trigger power to the seat heater module comes from the switch on the pink wire, connector C309, terminal C. The fuse power is the orange wire, terminal A.

Sounds like a bad switch unless there is a short to power.