I have a 1998 ml 320, since yesterday, dialing up from 1-4 on the fan setting, the motor gets louder and louder,...no leaves in the air ports....its def the motor, when its at 1 or 0, its winds down....but it still blows air..and works...just loud, with the motor noise., how do I get a closer look at it....whats the best way to look at what my problem might be...I have the glove compartment off and part of the dash, the noise is on the pass side front, right by the air port.