I have a Nissan Altima 2003, when the car is cold the car doesn't make that noise but as soon as I turn the heater on it makes a noise like whistling and raving noise that only sounds bad when I go from 1st to 3rd gear since my car is manual transmission but when I go to fourth and going fast is doesn't sound that bad.
Check the fan motor. Bearing could be going bad.
There also could be something in the fan itself. One
little leaf can make it sound like it is falling apart
February, 20, 2007 AT 5:07 PM
Sounds like some vacuum operating device within the heating system is going whacko or the fan is rubbing on the housing or a bearing mentioned earlier. You need to do some detective work and comeback with your findings.