On one of the TSB, Heater Blower is Noisy; it states the air intake below the windshield is obstructed by leaves etc.
There is another one, Knocking/Humming Noise at idle with A/C on.....I have attached the info on it.
I would also check the cabin air filter and replace it. I have attached that for you as well.
If you haven't every changed this.....you would be surprise how much debris can be in there.
I would look at the air intake area and clean that out really good. Then remove the blower and clean all of that area out and then the filter and see if that makes a difference. If not then check into the other TSB.
Cabin Air filter
1 Dust filter
Removal and Installation :
Remove cover panel below instrument panel. See: Body and Frame Interior Moulding / Trim Dashboard / Instrument Panel Service and Repair
Take off cover (2). Push the two remaining clips (3) in the direction of arrow for this purpose.
Pull dust filter (1) down and out (arrows).
Install in reverse order.
Knocking/Humming Noise at Idle With A/C On
All Technical Service Bulletins
Thursday, January 15th, 2009 AT 5:50 PM