Clunck when turing on defroster

My 2005 Rainier has experienced a hard clunk when I have turned on the heater/defroster. It only does it when the outside temperature is below 40 when I first start it in the morning or after a few hours. The dealer has checked the codes and finds nothing. Now that it is warm out it does not do this. I've had older Buicks which did this and was diagnosed as the clutch on the compressor sticking and then releasing with a clunk. I am wondering if this could be the same or possibly something else.

Thanks for any suggestions.

I would like to look into this issue further for you. In order to do so, I will need some more specific information from you. If you could please send me your full name, address, phone number, the VIN for the vehicle, current mileage, and name of the dealership that you are working with via private message, I will be able to take further steps. Thank you again and I look forward to hearing from you.

Tricia, GM Customer Service.