Ticking/Knocking noise coming from under driver's side dash when upper A/C vents on

[brasskey]

My A/C recently started making a noise under my dash. It only happens when the top vents are open. If you look at the video, it starts with the clicking sound and then stops when I change the airflow to the feet. But, when I change it back to the vents, the noise resumes. I assume there's some part under there that's at fault, but not sure where to start. Anyone have similar issues or know what might be the problem?

EDIT: It seems as though the sound is a lot louder on my phone and in person, so you might have to turn up the volume a bit to hear it better.

 

[roplusbee]

Possible Mix Door issue. Do your fan speed controls work properly? And is it AUTO Climate Control or Manual?

 

[FarFromStock]

I have been having an issue with ticking that sounds very similar to this and causes an issue with my two driver side vents blowing hot air at random. I will be driving along with the AC on and all of a sudden bam hot air blowing out at me. It is always only the two top driver vents that do this everything else is cold air still. If I stop then engine and restart the truck it goes back to cold air.

In regard to the ticking issue my truck has, if I increase the air temp on the driver side the ticking goes away. if I lower the temp it comes back and starts ticking. Try increasing the air temp on the driver side and see if the ticking goes away. if it does you may be going down the same path I am currently on.

I did a bit of research on my issue and also spoke with one of my good friends who owns a mechanic shop. I am going to try replacing the actuator for the blend doors that controls the driver air vents and see if it fixes my issue. I am actually picking the part up form his shop tonight. Will be installing it over the weekend.

Not sure if this is your issue but I have heard a lot of others mention this is a pretty common issue on our trucks. Just wanted to give you my input on a similar issue. Hope it helps. Good luck.

 

[brasskey]

I have been having an issue with ticking that sounds very similar to this and causes an issue with my two driver side vents blowing hot air at random. I will be driving along with the AC on and all of a sudden bam hot air blowing out at me. It is always only the two top driver vents that do this everything else is cold air still. If I stop then engine and restart the truck it goes back to cold air.

In regard to the ticking issue my truck has, if I increase the air temp on the driver side the ticking goes away. if I lower the temp it comes back and starts ticking. Try increasing the air temp on the driver side and see if the ticking goes away. if it does you may be going down the same path I am currently on.

I did a bit of research on my issue and also spoke with one of my good friends who owns a mechanic shop. I am going to try replacing the actuator for the blend doors that controls the driver air vents and see if it fixes my issue. I am actually picking the part up form his shop tonight. Will be installing it over the weekend.

Not sure if this is your issue but I have heard a lot of others mention this is a pretty common issue on our trucks. Just wanted to give you my input on a similar issue. Hope it helps. Good luck.

Possible Mix Door issue. Do your fan speed controls work properly? And is it AUTO Climate Control or Manual?

Thanks to both. The speed works fine and the noise happens in auto or manual.

I'll look into replacing the actuator.

 

[FarFromStock]

Wanted to add this to the post for reference. I replaced the actuator this weekend for my problem outlined above.

This is what the part looks like:

Here is the part box and part number. keep in mind I have a 2005 Tahoe LS 4.8 with manual ac controls not the digital readout. You might require a different part number based on your specific Tahoe.

You have to remove this black cover under the dash. There are 4 screws underneath then it just pulls free from the foot vents.

Once that

 

[FarFromStock]

Once the black plastic cover is removed it will look like this:

You can see the actuator hanging down in the middle of the photo close to the tunnel. Here is another close up photo of it.

All you have to do to replace it is unplug the red wire harness and remove two screws that hold it in. Then pull down and it will come out. There is a guide pin that must be lined up as well as making sure the D shaped slot lines up with the blend door (see photo above with the part and you will see what I am talking about) when you install the new replacement part. You can twist the blend door part it lines up with on the truck NOT on the actuator. In all honesty the most difficult part was putting the screw back on the black cover above the tunnel. There is not much room to get in there and you cant see it at all must be done by feel.

Hope this helps.