Now that the cold has set in my Air Con has started playing up. There is a strange sound coming from the passenger side of the dash when i increase the speed of the air flow. It is a rumbling sound and to describe it better it sounds like the Fan that blows the air is actually loose or something is rubbing on it. When the air flow spped is pointed to the lower value it is fine, it actually dosnt sound to be spinning at all, but when i put the flow speed in around the middle i get a loud rumble, and then at the fastest speed i get a very loud droning noise. How do i get at this fan to check it out because it sounds like something is rubbing off the blades.