2003 Hummer H2 "03 accord thermostat replacement" Questions

accord 2.4 exec on an 03 plate. The heated seat switch lights on bothe seats but neither get warm. Is there a relay that needs replacing? any help would be appreciated. According to the factory wiring

...03 Galant ES. When I turn the temp knob to cold and use the AC it makes a clicking sound, when I turn it back to heat it makes the same clicking sound and blows cold air most of the time. After a day ...