Knocking from under dash when key turned to on position

[Indfireguy]

Hey all just wanted to throw this out there just in case anyone experiences this and is looking for answers. I couldnt find anyone over the net that had experienced this noise.

Once key is turned to on position there is a real loud knocking sound, it persists even once truck is started, and lasts for about 10 seconds. It sounds as though its coming from behind glove box. I went to dealer and lucked out describing the sound, the technician new right away what I was talking about.

It was the Actuator. It is apparently pretty common in colder climates, the cold causes a slip which causes the knocking noise. Once it catches up the noise goes away. Anyway all fixed and problem solved. Actuator replaced, full warranty.

 

[RatedSVT]

Actuator for what exactly?

 

[Hocker52]

Maybe the one for the A/C , Heat and defrost. Mine wasnt making noise. But when I turned on the defroster it wouldnt heat up on the drivers side. They had to replace it

 

[Indfireguy]

From what I understand talking to the technician, is has to do with the fan for heat/climate control. There is an independant little motor that causes the actuator to turn. Apperntly there is a fair bit of tension involved in it. So when the actuator is shot, as its trying to catch up it slips, causing the loud knock. Once it catches up and fits into the groove it stops. If anyone can make better sense of this feel free to add, as im not 100% with the details. That's the best I can explain it from what i remeber.

 

[RatedSVT]

Well I dont have the knock, But just wanted to know for future reference incase it does oneday.

 

[Indfireguy]

For sure that's why I put it up. I searched all over the net with no luck trying to diagnose the issue. Now theres a referance point.
I didnt want to show up at the dealer trying to explain some phantom noise, so I also recorded it, just in case the noise decided not to appear once with the tech.

 

[dataustin]

Truck just started with the 'nocking' sound from behind the dash. Only seems to happen when truck has been sitting for a while. Unless anyone has any additional feedback, sounds like I have a bad actuator.

 

[scarrjack]

I had this happen a few months ago, dealer fixed it under warranty.
According to the invoice the dealership called it a "blend door actuator." The left side actuator was faulty, they had to remove the dash assembly to replace it, reassembled it and has been good ever since.

 

[Boss Hoss]

Mine went through 3 of them.

 

[Ricky B]

It's the blend door. My 2011 was doing it for about 6 months before it finally quit working. Of course the day it quit was the day we had a high of minus 2 degrees. Froze my ass off driving it to the dealership.