blower fan noise

i am trying to help my father trouble shoot something on his colorado. First time posting.
he owns a 04 Colorado, with the 5 cyl engine
he is complaining of noise when the blower fan is on in the car (on a low setting). Said it sounds like debris is in there. He has taken it to the dealer more than once, who for a small fee of $15 vacuum out the blower intake tube. He would like to learn how to do this on his own to save $$ or if there is another underlying problem.
Any takers?

Mike

Hey Mike, I'm not sure if it's the same problem or not, but my '05 colorado had the heater fan making a strange noise and pretty soon it only worked on high. After a second trip to the dealer I discovered that there is a wiring connection under the dash above where the passengers toes usually are. Good place for a connection. Anyway, this was loose and you could see the plastic was turning color from the loose connection. The dealer replaced the connector and it solved the problem. Might be something totally different but if it quits working at some speeds, keep that in mind. Joe

Mike, did you and your father ever figure this problem out? I am having the same one and just was curious. Thanks.