Has anyone experience any ac/heater whinning. I have a 2004 screw cab lariat and it seems that when the temps gets around 40 or below and I turn on the heater a whining noises comes from the dash for about 3 seconds and it fades until it's not heard anymore. After the truck warms up it doesn't happen any more, until it sit's for a while and again the temps around 40 degree. I was told by the service manager that it's some sort of heater doors that open and close and the whole dash will have to be taken apart. But, by the time I get to the dealer (15 minutes away) it does not happen. Some advise please.