strange snapping or popping sound behind dash associated with temp control movement

When I move the heater temp control knob either way, shortly there after I hear a snapping sound that will last a few seconds or many seconds. I'm afraid it has to do with the heater diverter door where the mechanical connection to the door is broken or stripped out. I saw a you tube showing a Titan with the dash completely removed to gain access to the heater/ evaporator assembly that had a plastic arm broken where the owner didn't have heat because the door was unable to move. I'm thinking this is my problem. The fix for this guy was a complete heater/evaporator assembly. All I saw after that was $$$$$$$$$ to fix my truck. Has anyone else experienced this problem? And what was your fix?