Hvac resetting itself at startup

[Sean J Blackburn]

Ever since I have owned my 2010 1500 (about 6 years), at startup the hvac has an issue. I just recently realized this is not normal. At startup, regardless of where I have selected the vent position, the air always comes out of the floor vents. As soon as the truck starts blowing air out the floor vents it will correct itself and switch to whatever position I have selected.

All positions work, it's just that every time I start the truck the hvac has somehow set itself to the floor vents and then quickly switches to whatever position I left the settings at.

Does anyone know what causes this or how to fix it?

 

[Jeepwalker]

Do you ever hear it trying to recalibrate (a couple times) after it's shut off?

Ideally, if you knew someone with a good scanner which they could look at the HVAC...run it through it's paces, to make sure there isn't a failed damper or broken door (like the inside/outside air blend door or actuator).

 

[crash68]

Does anyone know what causes this or how to fix it?

If the HVAC system is returning the settings when you turned the truck off without having to push any buttons, then the system is working as normal. With the electric actuators, they will return to a default position several minutes after the vehicle is shut off and begins to "go-to sleep".

 

[Jeepwalker]

I think he's saying the truck HVAC *doesn't* return to the same settings upon start-up. My truck stays on the setting it was at previously. If it was on AC before, that's what it start up with next time. I'd be looking for a flaked-out hvac blend door actuator, bad grounds to the hvac controller, crapped out blend door hinge, or flaky controller (in that order).

The reason I ask if the system 'hunts' is .....normal operation is the HVAC blend doors will periodically swing full open and full closed. I forget, it might be upon vehicle shutdown. That way the computer knows (remembers) where the endpoints are, so next time if the doors need to be, say, 36% open to achieve the desired temperature, it knows where 36% should be.

But if there's a fault in the system, it will attempt to 'recalibrate' like normal, but, when it can't find an end-point (say, a broken door) it will attempt a couple times more. After repeated failed attempts it will stop 'hunting'. It knows something's wrong.

The outside air damper is one which you might not notice any temperature difference (like lack of heat) in AZ, but could trip up the entire system. Not saying that's it, or even if there's a fault, but articulating the damper with a 'good' scan tool, or even reading HVAC codes (and a quick set of eyes on the damper itself with a flashlight and careful eyes) should yield some answers. Some owners have had controllers flake-out too. Or, sans scan tool, just paying very close attention to the sounds during calibration can tell a lot (when ya know what to listen for). Try that and see what you discover. Our Jeep's OA blend door is half broken from it's hinge ...been like that for yrs (I've propped it 'closed')...and it always reverts to AC upon start-up...even if it's -20F outside. LOL.

You might also try unhooking the truck's battery overnight just for kicks, b/c it doesn't cost anything, and re-hook up tomorrow and see if it resets the HVAC module. May not make a difference, but you never know. Trucks and modules get whacky sometimes. And make sure the truck's batt connections are good and body-to-battery ground is solid-good.

 

[crash68]

I think he's saying the truck HVAC *doesn't* return to the same settings upon start-up.

Right in the OP's second paragraph:

All positions work, it's just that every time I start the truck the hvac has somehow set itself to the floor vents and then quickly switches to whatever position I left the settings at.

The damper actuators are electric and do not have any form of spring return.
If you sit in the truck for a few minutes after the truck goes asleep, you can usually hear the actuators moving on their own. There has been multiple threads on this forum about this with people wondering what the noise is.

 

[Sean J Blackburn]

Right in the OP's second paragraph:

The damper actuators are electric and do not have any form of spring return.
If you sit in the truck for a few minutes after the truck goes asleep, you can usually hear the actuators moving on their own. There has been multiple threads on this forum about this with people wondering what the noise is.

So just to clarify, this is normal, intended functionality? Thank you for your help!

 

[Sean J Blackburn]

Hey jeep walker,

The settings do return to whatever I had them at. For example, if I left the truck on ac, recirculation, blowing at my face, the truck will return to that a few sec after starting. However, when I first start the truck it will always blow out the floor vents before switching back to whatever position I last used.

 

[Jeepwalker]

Oh ok. Sorry, I was thinking it 'didn't' revert back.

The damper actuators are electric and do not have any form of spring return.

I know that. I was just trying to explain how the HVAC computer does regular calibration stoking of the dampers (electric motors) to each end-point (full open/Full Cloesd) and it the HVAC module ...basically a little computer, determines where full open and full closed is and can calculate percentages in between as needed. It's good to know and listen to when ya hear some squeaking and actuating going on.

The sequence of operation is outlined in the service manual.