NBS 2007 Sierra No Defrost

jon99z71 · November 27, 2018

Hi,

I have a 2007 Sierra 1500 SLT and I cant seem to get the defrost to work anymore. The controls on the dash all seem to function correctly and I can select where I want to divert the air however it will only blow at my feet and a bit at my face. Temperatures, a/c and fan speeds can be changed with no issue and the dual climate controls all work as well. Just can't get the system to divert air where I select it. Went through other forums and Google searches and have had enough guys saying to turn the key on and off facing a southern direction and then get out and walk around the truck clockwise twice while tapping your head..... Crapola!!! Just looking for some good educated ideas as to what it could be, I'm sure this issue has come up in the passed. I'm assuming it has to do with the damper actuator or possibly as simple as a recalibration.

Any help would be greatly appreciated.

Thanks

James Elliott · November 27, 2018

Hi,
I have a 2007 Sierra 1500 SLT and I cant seem to get the defrost to work anymore. The controls on the dash all seem to function correctly and I can select where I want to divert the air however it will only blow at my feet and a bit at my face. Temperatures, a/c and fan speeds can be changed with no issue and the dual climate controls all work as well. Just can't get the system to divert air where I select it. Went through other forums and Google searches and have had enough guys saying to turn the key on and off facing a southern direction and then get out and walk around the truck clockwise twice while tapping your head..... Crapola!!! Just looking for some good educated ideas as to what it could be, I'm sure this issue has come up in the passed. I'm assuming it has to do with the damper actuator or possibly as simple as a recalibration.
Any help would be greatly appreciated.
Thanks

Could be a relay or fuse too not letting the flap direct air flow to where u need it

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kickass audio · November 27, 2018

If these are anything like my envoy I had you can try to pull the fuses for HVAC and leave them out for a little while (like 15-20 minutes) and put them all back in. DO NOT start the truck at all, leave it sit for another 5 minutes. It would trigger the HVAC system to sweep the actuators from one end to the other. If doing that doesn't help then you more than likely have a stripped gear or a broken motor on the actuator.

Supreme Pizza · November 27, 2018

Maybe an obstruction? A pen fell down though the defrost vents, and are blocking the moving parts?

jon99z71 · November 27, 2018

5 hours ago, kickass audio said:

If these are anything like my envoy I had you can try to pull the fuses for HVAC and leave them out for a little while (like 15-20 minutes) and put them all back in. DO NOT start the truck at all, leave it sit for another 5 minutes. It would trigger the HVAC system to sweep the actuators from one end to the other. If doing that doesn't help then you more than likely have a stripped gear or a broken motor on the actuator.

I assume you need to have the key in the on position with the fuses out? I saw a YouTube video of a guy doing something similar on a 2005 Sierra. Not sure it'll work the same on the new body...

jon99z71 · November 27, 2018

5 hours ago, starman8tdc said:

Maybe an obstruction? A pen fell down though the defrost vents, and are blocking the moving parts?

Its certainly possible, although I dont leave anything on the dash unless something finally found it's way from the first owner 9 years later..

txab · November 28, 2018

A re-calibration may fix you up. Try disconnecting the battery for
a few minutes. Reconnect it. Or remove the HVAC/ECAS fuse for a minimum of 10 seconds.

Re-install the HVAC/ECAS fuse.

Then turn the key to the on position, but
don't start. Don't touch the HVAC controls. Actuators should begin to move, changing positions.

Air flow may change outlet points during this time. Wait
about 1 minute. Turn key off. Key out plus opening and closing the door can
make a difference as the vehicle controls see this as "cycle"
completion. Next start the vehicle and drive it a short distance and see
how it performs. You may indeed need to replace an actuator.

jon99z71 · November 28, 2018

9 hours ago, txab said:

A re-calibration may fix you up. Try disconnecting the battery for
a few minutes. Reconnect it. Or remove the HVAC/ECAS fuse for a minimum of 10 seconds.

Re-install the HVAC/ECAS fuse.

Then turn the key to the on position, but
don't start. Don't touch the HVAC controls. Actuators should begin to move, changing positions.

Air flow may change outlet points during this time. Wait
about 1 minute. Turn key off. Key out plus opening and closing the door can
make a difference as the vehicle controls see this as "cycle"
completion. Next start the vehicle and drive it a short distance and see
how it performs. You may indeed need to replace an actuator.

Thanks txab,

I'll give that a shot later today. I'm thinking I still have an issue with the actuator itself because I've had the battery disconnected a few times in the passed for durations of time for other reasons and have never noticed the defrost working again. This has been an issue for at least a year now, but so far I've managed to keep the windshield clear. I will like to sort this out however.... What all needs to come apart to access the actuator if needed. My truck has the full jam interior, leather, full console, etc...