I assume you've already checked the fuse. Buy a new heated seat relay, then... 1) Park the car somewhere quiet. 2) Turn on the ignition (but don't start the engine) 3) Starting in the OFF position, SLOWLY turn up the dial for the driver's seat. At some point, you should hear a click from the relay under the seat. If you hear no click, replace the under-seat relay and re-try the test. If you still get no click, it's a wiring problem. If you do hear a click, but the seats don't noticably heat up within 2 minutes on maxiumum setting, replace the relay and re-try the test. If they still don't