Hi all,
First time post and new guy. I had this problem and did some research online. About 95% said the actuator was bad and needed to be replaced. Its kind of a pain to replace the actuator and costs about $50 or so. Saw the following online and tried it. Low and behold it worked. It seems the actuators get stuck sometimes when the battery is disconnected and they go some kind of reset or recalibration. So, all of a sudden you find it starts acting funny or just stays in one vent and wont change. I had this very same problem, and this fixed it.

I had a similar issue. Air would only blow out of defrost vents after I replaced my battery. But this worked for me:

1) Unplug HVAC fuse for 10-30 seconds
2) Start truck
3) A/C comes out defrost - wait about 10 to 15 secs. If not, cycle the distribution **** ( for lack of a better term), the one that selects which vent it comes out of. I had to do this before it would cycle.
4) A/C then starts coming out the floor vents for about 5 seconds
5) A/C then starts coming out the dash vents.
6) While the A/C is coming out the dash vents, turn A/C OFF (otherwise it cycles back to defrost for good).
7) Turn truck OFF
8) Restart truck and it should work fine

I did this and everything works fine now. Dont know for how long, but its better than fighting with the actuator, panels and pitching out $50. Good luck.

 

I tried this and it worked!

 

1. Quote:

   Originally Posted by Stormyj

   Hi all,

Did you leave out the fuse in when you started the truck? Or put it back in before start?
Thanks

 

Worked on my 2015 Silverado, too. Thanks!!!!!! It's a relay that I removed, though, not a fuse. Number 67 in my panel.

 

This dose not work always. I tried over and over no success.

 

I've done these steps. As long as I leave the fuse out, it will continually blow hot air out the vents. As soon as I put the fuse back in, it goes back to defrost. Any suggestions

 

First-time poster so bear with me.

Have you tried the reset where you pull the fuse and force the computer to relearn the blend door positions? This guy explains it pretty easily
It worked for me temporarily. You can also make sure your head unit is set to the right vehicle configuration.
I have not tried the process mentioned in this thread specifically other than I turn my vehicle off with mode set through front vents all the time. The air still randomly switches to defrost only, and sometimes I can switch it back right away other times it won't switch back for twenty minutes with me cycling through the controls over and over. I can't find a pattern. I've checked and cleaned the blend door actuator under the driver's side which controls vent position. It is functional. I replaced the blend motor for temp control under the passenger side. The mechanic reset everything via computer and it worked for about a week. AC compressor is less than two years old and the system was recharged a month ago with no detectable leaks.

I've even replaced the head unit. After replacing the Doorman (no GM available) head unit the system worked great for about a week. Now again it switches to defrost randomly. I pulled the battery cable during some electrical work and had to reset everything again works for a while then the issue comes back.

I am thinking I need to replace the head unit again or there's something fouling up between it and the vehicle computer causing it to switch to defrost randomly.

 

Tried this after recently changing my battery, and it worked exactly as said. Thanks for the post and the help.

 

YES! It totally worked. Thank you!

 

This works 100%. You saved me from buying an actuator and a lot of unnecessary work thank you.