How Does Blend Actuator work
 

I have a 2006 2500hd chev with dual sliding temp controls. The driver side will suddenly move from cold to hot as you are driving along. It won't go back to cold until you shut off the truck and restart. So something is telling this blend actuator to move right? If it gets a false signal from the sliding switch it could do it right or wrong?

So I am looking for theory of operation?

Blend motors are nothing more than step motors. They have a hi limit as well as a low limit and can be "told" to stop anywhere in between.

The processor in the temp control "reads" the user settings and then adjusts the doors accordingly by 'stepping' these motors to the correct location/position.

If your door suddenly changes positions just out of the blue, I would first suspect a door slipping on it's axle or a bad gear/sticky action within that door actuator.

However, since it correctly 'resits' when powering up, think I'd lean towards the door itself or a chaffed ground circuit from the control head to that actuator.

Does it do it when the truck is parked, or does it always happen only when you are moving (vibration)?

Allan

Thanks for answering. It doesn't occur very frequent but it was always when driving. I did the reset procedure on HVAC/ESC on Sunday and it hasn't failed since. Sadly I went into Chev service to seek advise and after talking with me they said they would replace blend actuator. They said there would be no fail info to pull. Their exp. said 90% sure on blend actuator. Cost would be 2 hrs labor+$140part. They showed me where it was a little info on how to get it out.

Sadly I lean toward the electrical glitch idea, maybe I can pound around in that area. Is there logic that would explain always going to full heat instead of half way heat?

Wonder what chev would do if i paid the $400 and it wasn't fixed? Say sorry but we will have to explore some more?

I have a semi similar issue on by pickup. My AC will be doing just fine and then all of a sudden I hear what I think must be the blend door closing and all I get is hot air out of the vents. I know that the AC is working, but it just isn't getting out of the vents. It does tend to 'reset' after it has sat around a while and I can get cold air again for a while, but I have no way to know how or why this 'reset' occurs. My issue is that I'm not sure if the root cause is the actuator itself (doesn't seem like it since it works sometimes) or the control module (again doesn't seem right since it works sometimes.

Where would I look for the ground in this circuit? I want to say that I saw something in another post saying that there was a ground on the frame somewhere under the driver's seat??? Any help is appreciated.