A/C Fan Speed Varying

06-1500HD · April 16, 2015

The fan speed changes intermittently in my truck when the a/c is running. It seems like its going from outside air to recirculate on its own. I always run outside air and when it does it I'll hit the recirculate button and nothing changes. Then I'll hit the recirculate button again and it will go back down to where it was. When it changes on its own the recirculate light does not light up until I push the recirculate button. The fan speed setting never changes on the controls. Anyone else having this issue? I have automatic dual climate control and have it on sync but not automatic so nothing should be changing.

Dadof2 · April 16, 2015

Not sure this will help but after 11k miles I just learned something new about mine. I generally run my A/C on low temp with fresh air set and the passenger side sync. When the temp is set on "low", recirculate turns on automatically without the recirculate light coming on. If I turn the temp knob Up to show temp of 60, or higher, it goes back to fresh air. I keep my temp set to 60 or higher to make sure it stays in the fresh air mode. Hope this makes since.

06-1500HD · April 16, 2015

Thanks for the reply. Unfortunately I pretty much always run it at 70 deg and that is when it does it. Rarely run it in low.

khoeman · April 17, 2015

The fan speed changes intermittently in my truck when the a/c is running. It seems like its going from outside air to recirculate on its own. I always run outside air and when it does it I'll hit the recirculate button and nothing changes. Then I'll hit the recirculate button again and it will go back down to where it was. When it changes on its own the recirculate light does not light up until I push the recirculate button. The fan speed setting never changes on the controls. Anyone else having this issue? I have automatic dual climate control and have it on sync but not automatic so nothing should be changing.

I think I noticed this on my 14 Sierra yesterday for the first time. I just recently had the new headlights installed and had the BCM updated as well. I was wondering if it was maybe due to this update as I've never noticed this before.

stevev · July 19, 2015

My truck does this too when running in manual a/c mode and I don't touch any of the buttons or dials. The speed will just vary up and down on its own.

Silverado4x4 · July 19, 2015

I don't have auto climate but mine did this also. I went down to my dealer last week for an oil change and he said there was an update on this problem, they did it when it was in for the oil change, problem is solved. It also fixed once in a great while when I start the truck with the climate control off and then turn on the climate control while riding down the road it wouldn't come on the display would say "off" nothing worked till I shut the truck back off then restarted with the fan on then everything was fine, like I said it would do it once in a great while.

stevev · July 19, 2015

I don't have auto climate but mine did this also. I went down to my dealer last week for an oil change and he said there was an update on this problem

Is there a TSB or bulletin number for the update on your receipt?

gone_fishing · July 19, 2015

Is there a TSB or bulletin number for the update on your receipt?

Also interested. I'm always in manual mode for my HVAC controls. This is when I noticed the varying speed. I'll have AC on, set at 70, recirculate off with fan speed all the way up and set to come out dash vents only. Fan will be at a given speed then after a few minutes go down a little. A few minutes later it will go back up. This will keep repeating.

Tman68 · July 19, 2015

I had this issue with my 14 gmc, it was all manual controls, my 15 has not done it yet with the automatic settings...

Silverado4x4 · July 21, 2015

Is there a TSB or bulletin number for the update on your receipt?

I don't have a number for the update as when they did the oil change on the truck the service manger just told them to do the update on the climate system but they didn't put it on the receipt probably because there service computer systems went down when I was there so they didn't enter it just the oil change was on the receipt.

Call or go to your dealer and ask them about the update it was on the Chevrolet main frame, they always check it to see if there are any updates for the truck everytime I bring it in for the oil change. I also told him about it what it was doing but he was already checking for any updates so they put it in.

stevev · July 21, 2015

Ok thanks for the update.

stevev · August 22, 2015

Is there a TSB or bulletin number for the update on your receipt?

just to quote myself, I had my truck in for service a few weeks ago, and they were able to do the update for the varying a/c fan speed. On my paperwork, it says "update for blower concern WCC99B28"

06-1500HD · November 3, 2015

I took mine in and they said it is operating as it should so now the fun begins. I guess the unit constantly doing what it wants is standard operating procedure for these trucks.