On my way back home from my parents house, which was to be about a 10 drive, my wife, daughter and I hit the road around 5:15am.
The temperature was in the low to mid 40's, so of course I turned the heat on inside the car.
About an hour and a half into the ride, I head this noise and had NO CLUE where it was coming from...
It initially sounded like it was coming from the passenger side door speaker.
I thought..."Damn...now the amp wants to go...but its practically brand new..??"
I pull over, unplug the phone charger from the ashtray, noise still there...
I go and put my ear next to the passenger door speaker, nothing from the speaker but noise still there...
I get back in the car and im trying to figure out where the noise is coming from..im pressing on dash panels, turned the radio down/off, nothing seemed to stop the noise, and I couldn't tell where the noise was coming from.
Suddenly, out of no where, it just stopped.
I turned the radio back on and continued to drive.
Now, here I am in the last stretch of my drive, about 25 minutes from my home exit, and the sound comes back.
Im driving and im thinking...what is on right now...
I turned off the heater and boom, the noise stopped!
I turned the heater back on after a few minutes, it was quiet and sure enough, within a few moments, the noise came back. I'm like Jesus-really!?
I get home, park it and just wanted to relax after the 10 hour drive.
It sits for a few days and I start it and turn the heat on and ran the heat for about 20-30 minutes and the noise never came back, however, I can hear a faint noise, which im assuming is the blower.
FYI: While the noise was occurring, the heater still worked.
I'll address it when it seems that the problem become more consistent.
Thoughts?

 

What kind of a noise was it? I wonder if it's the blend door motor (if that's what it's even called).

 

I second that question on the type of noise... I've had instances when a little leaf sneaks in there, and whenever the blower motor runs, there is noise. If the leaf temporarily shifts, the noise goes away. Just a wild guess, as a starting point, because if it was a bearing in the blower motor, I'd expect a more consistent squeak.

 

Funny this post came up today.... I started up my Ford Ranger PU this afternoon for the first time since Christmas and heard a "high pitched whine" coming from the dash area so I turned off the blower and the whine went away so I pulled out the blower fan and there was a small twig along with a few leaves on the blower duct....... Got out the shop vac and cleaned out the housing, put everything back together and the blower is now running "noise free." This was an EZ to do 20 minute job on the Ranger.
TRY THIS: Turn on the blower to "high" and cycle through the controls from floor, vent, defroster and see if the noise takes on a different tone...... Hopefully if there is a leaf in the blower housing it may just break up and blow out. You may also want to pull out and change the cabin filter too.

 

Love this place!
Thanks guys!
To answer the question, while I'm not the best descriptive writer, the sound can be best described as a kind of high pitched whining noise. Nothing at all like a bearing grind or a metallic noise.
Just a higher pitched, consistent noise.
The closest thing I've heard like it, was a noise I recall hearing back when I had an 89 Maxima with a Bose sound system.
I replaced the head unit and used to get a little bit of feedback noise..a pitchy whining noise..
Sorry for the poor explanation everyone.
I know the cabinet filter is in the glove compartment, where would the blower be?

 

The blower motor is located on the front passenger side and it is on the underside (bottom) of the plastic blower box....... The blower pulls out from the bottom.