whirring noise behind the dash?

[thedynoguy]

A strange whirring noise has started behind the dash (sounds like behind the temp controls). It begins when the truck is up to operating temps, and continues whether the heat is on or off, the stereo is on or off, and doesn't change with the heater fan speed. I'm about to make an appointment at the dealer to get it looked at, but I'm afraid they won't give the truck enough time to warm up for the sound to start up. Anyone heard of this before?

[mo powerstroker]

I get that sometimes with my 09 it just started doing it like a month ago I thought at first maybe the cold weather was some of the reason. But it probably isn't.

[nthe10s]

My 08 does this too. Almost like a vacuum leak or whirring like you said. Problem is it doesn't do it all the time. Think it could be from the "rapid heat" heater in the heater box?

[thedynoguy]

I don't have rapid heat... mine doesn't do it all the time either, but if the truck runs for half an hour or so, it seems to start, and stops when the key is turned off.