03 monte heater noise

i have an 03 mc ss 3.8 and every morning as i start it up and proceed to turn on the heater it begins to make a sort of rattling noise from under the hood. I have yet to even troubleshoot the problem so if anybody has any comments/suggestions i would appreciate it. THANK YOU

You don't hear the noise in the cabin at all?

I would say something might have fallen into your defroster vents and is being hit by the blower motor, but if you can't hear it inside :dunno:

Its might be a leaf or paper flapping in the cowl screen or the bearings in the blower. Try hunting the noise down and let me know.

The noise can be heard from inside the cabin but is much louder from the outside of the car. it begins a couple secs after switching on the heater and lasts about 25-30 secs and returns about a minute and a half to 2 mins later. Still havent tried to hone in on the location but def will tomorrow morning. Thanks for your comments.

One last comment, the noise does seem to come from the blower (maybe the bearings). Just wanted to know how to go about making sure thats the problem and how difficult would that be to fix it myself ? Thanks again for all replies

It sounds like the blower motor is out of balance. This could be caused by leaves/debris in the blower impeller, or worn bushings in the motor itself. If you pull the motor down, and there's nothing in the impeller, it's time for a new blower motor.

Yeah, I've had this same problem with my 2003 Monte Carlo and if finally stopped after about 6-months to a year. Then after the noise went away the controlls stopped working that controlled where the airflow came out. Any solutions please let me know as well.