It started out as a very quiet clicking sound a couple months ago and as of yesterday it sounds like a giant cell phone is vibrating under the dash right behind the radio. It happens even before the engine is turned on while the key is in the "on" position. It will last anywhere from 2-15 seconds at a time and normally stop after driving for 5-10 minutes. It seems like if I turn the AC off as it is happening it will stop 2-3 seconds later but I have not done enough experimenting with this to know for sure that it is affecting it. I also don't think it has happened while the AC has been turned off, but again, not enough experimenting to know for sure.
Help me out TexAgs, what's the problem?

So if you turn the AC fan off,the noise stops?

As far as I can tell, yes. It is my wife's car so I have only had a 15 minute drive to troubleshoot. Everytime the sound starts I would immediatly turn the AC off and the sound would stop 2-3 seconds later but I was only able to copy this result 2-3 times. Sometimes the clicking would only last 3-4 seconds with no intervention so I don't know if turning the AC off made a difference or if it was just coincidince.

A/C blower motor/fan. Seems like the housing or mount is loose if it's not consistent. Bumps in road probably shift it.

Could be a bad bearing or a leaf in the wheel etc.

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Bumps in road probably shift it.

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It happens immediatly when turning the car on and will go on and off even when the car is not moving.

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Could be a bad bearing or a leaf in the wheel etc

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It's definitely coming from under the dash close to the radio and glove box. It sounds like what I would imagine gears slipping over each other sounding like.
From what I have read online it could be something related to the gate that mixes hot and cold air for the AC. I'm going to have my wife drive around later with the AC turned off and we will see what happens.

I had a similar issue and posted here about it a year or so ago. It was the blend door actuator in my Impala. Could be a similar actuator (I believe there are 3 locations in my Impala's AC system that use them.)




[This message has been edited by AgResearch (edited 10/12/2012 11:35a).]

were you able to replace them on your own or did you go to a shop?

I replaced it on my own. Mine was located behind the glove box and had three 5.5mm screws holding it so it was an easy location.

You'll need to match the actuator position to the old one.

The picture above is what a Chevy one looks like. Your's should look similar since there's not much you can do to change an actuator.

[This message has been edited by AgResearch (edited 10/12/2012 11:34a).]

It looks like there are three servos on the 04 4Runner so I'll check those out and report back. Thanks