Q: What makes the heating system not switch back and forth from heat to air? on 2002 GMC Yukon

Rookie cbe0621eac06868b3efe0d8d1d3611e23c60d3114864ea2ec19a68cfbd3eebab
If you have the heat on will not switch to air but if you switch and then shut the engine down for 3 or 4 hours it will switch.
(1) Answer
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Sounds like a possible temp/blend door actuator. It can be scanned with a professional scan tool to verify the fault.
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