Defrost Module Actuator

[pkpxavier]

2003 1500HD...had strange ticking noise from under dash lasted for about 6 months...found out that if I threw it to defrost and then back to vents it would stop....well now air will come out of the floor when the truck is first started....then only out of the defrost after about 5 mins of running. The parts guy at our GM supplier told me it was the defrost module actuator...where is this and how do I change it out?...or is this even the problem?

 

Thanks for the help in advance...

 

Adam