I've noticed an arrhythmic knocking or tapping noise coming from under the dash towards the passenger side of my truck. This starts when I first turn the key on and tends to go away after a few minutes of driving. It occurs with the engine on or off aswell as with the a/c fan on or off. Same goes for the stereo being on or off. With all of these factors ruled out, i'm not sure what could be making the same sound down there. There shouldn't be anything else moving correct? No critters in there either, especially not for 6 months. The truck is an '05 gmc regular cab with dual zone manual climate control. 5.3 automatic, manual windows and locks if any of that matters. Any guidance is appreciated before I go on a needless witch hunt. Thanks

 

blown speaker rattling?

 

It's a a/c door actuator binding. It can be one of 3 or 4 .like the temparature door, the blend door or the mode door actuator. IT's bad and it's trying to wind continusly.

 

Much appreciated. Could something have been sucked up in there to do this? It's done this the whole time I've had it

 

there may be an update for the HVAC controller software. the noise usually happens in full cold or hot. when its making the noise, change the temp just a little and see if it oes away. if it does, it needs a reflash