Question about 1999 Chevrolet Silverado 1500

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Heater/AC fan diverter door knocks

The Heater/AC diverter door knocks about 30 times when I turn ignition on and after I turn it off. It is mystery. Is the electric and vacuum system?

This started after I disconnected battery to charge it.

It is located on firewall right behind fan. I can reach up in there and touch it.

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  • 29 Answers

Change the heater control valve.

Posted on Apr 22, 2009

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