Some people have reported a clicking noise in the transfer case when it's low on fluid, so check the level. If the level is fine, use a screen to drain the fluid through and watch for metal flakes. If you find them, the transfer case would need to be rebuilt.
could be the water pump. maybe radiator
A clicking noise from the dash on a 2003 Mercedes Benz might be the flasher for the turn signals. Sometimes the flasher will make a clicking noise if it is about to go out, to let the driver know it is time to replace the flasher relay switch.
heat/ac actuator
Sounds like a wheel bearing to me.
if you have a bad axle they will usually make a clicking noise when turning
I have same issue except I am on cold and get clicking when attempting to go to heat. also rear areas have heating or cooling
The 2003 Chevrolet Silverado-1500 has a V6 engine.
The 2003 Chevrolet Silverado-1500 has 12 valves.
The 2003 Chevrolet Silverado-2500HD has 16 valves.
The 2003 Chevrolet Silverado-1500 has a 5-speed manual.
The 2003 Chevrolet Silverado-1500 has overhead valves (OHV).
The 2003 Chevrolet Silverado-2500HD has overhead valves (OHV).