I am having trouble with my heat in my 2003 tahoe heat only works on one side.

 

Try this. Start vehicle, turn driver side to max cold, turn passenger to max hot. Turn off vehicle. Restart and turn driver side to max hot and passenger to max cold. Turn off vehicle. restart and set to normal settings. Worked for me.

 

Might need to check the actual links that attacht to the control doors. Some times the links disconnect from the heater control door actuators and levers.