Hey you genius mechanics!
2002 Chevy Trailblazer. No Codes present or in history
I've had problems with my mix door actuator (temp), and my mode door actuator since I bought this 9 mo ago. they seem to stick. . By sticking I mean they would go all the way to open or close when I did a reset and they then wouldn't move. I did replace the mix one and nothing changed. same thing.
I have a bi-directional scan tool and long story short, it says it is calling for it to move when I send command but it is not moving. I back probed 3 of the 5 wires. all tested good, ground, 5v and 12v. didn't do the signal wire cause not sure what to look for and didn't want to brick my HVAC controller.
But Here'* what I found and don't understand. I removed both actuators and with key off, I could turn the door flap with my fingers. But when I start the engine they are tight as can be. won't budge, not even with pliers. anyone know what the heck this is?? My HVAC controller is electronic climate control. No vacuum lines as far as I can tell.
and lastly, the passenger has own controls for temp and it WILL change from hot to cold on that side.
???????

The ducts can get warped and keep the door(*) from opening and closing correctly.

any idea why I would be able to move it easily while the car was not running? just curious.
I think you're right about being warped. that or something is broken.
I'm waiting for a warm day to do more troubleshooting.

If the HVAC head is commanding the actuator and the signal is present then the actuator should actuate. Check the output of the module while using the scan tool to command it.

will do. thanks

Update.
I worked on it yesterday. Sorry but I actually forgot to check the output of the HVAC module, but that will be easy since I have the dash trim off, so I will get to that soon.
However, I did find something. When I wiggled the connector for the temp actuator something kept clicking under the center console. That'* where the module for rear auxiliary HVAC/RSA is. RSA is rear seat audio. so I guess I have a bad connection on the actuator? It still wouldn't move though when I changed the temp on the HVAC module and wiggled the connector.
So anyway, I had to get heat and here'* what I found and did. Like I said earlier, I could move the door flap with my hand with the engine off. but with the engine running I couldn't budge it. I forgot to mention it is spring loaded, so when I moved it by hand with engine off, when I let go it would spring back all the way. and that position is cold air, no heat.
so I tried something, I turned it the other way and held it there and started the engine, put the fan on high, let go of it and it stayed there! but if I either turned the fan down, or shut off the engine it would spring back to the cold position. some kind of suction or vacuum is holding it there maybe. So to get heat temporarily I turned it by hand all the way to the heat position and put a small pair of needle nose vice grips on it to hold it in place for now. so it is in the full heat position. I can still turn the fan speed up or down and change which vent it'* coming out of. So that will do for now if not all winter.
I still wonder if there is something wrong with the door flap because you can't budge it with the engine running, so I don't think the actuator could move it anyway. I may have to pull my dash this spring to get to the whole door module thing.
I still want to check the output of the HVAC module soon, so I will let you know what I find with that. And I have to repair that connector, which won't be fun because it'* so tiny, it will be hard to get the wires out.
but if I can straighten all that other stuff out then I will know if it'* my door flap or not.
Thanks for the advice and help!

Interesting, thanks for the update!

Hey everybody,
I finally got to repairing my actuators. So I'll start from where I left off. new actuators didn't help. new HVAC control module didn't help. reset it a million times, no luck.
Now the mode is going bad. I have defrost and floor only, no vents.
So I tore the dash out. the doors were sticking. So I lubed and greased everything and they all are moving smoothly now.
Here'* the problem, I put the actuators in with the dash out, right, so I could see everything. when I put new actuators in the mode and blend door and turned on key and module started it'* learning, mode actuator now works ok but it moved the blend actuator half way and then back all the way and then wouldn't move anymore. I have 4 new actuators and they all do the same thing! I even put the old HVAC module back in and nothing changed.
I took 3 of the new ones apart and checked the potentiometer in them and set the shaft in the middle and then set the potentiometer in the very middle, 4 ohms reading from one side to the middle and 4 ohms from the other side to the middle and put them back in and they all did the same thing. the module does it'* learning thing then takes the act. all the way to one end and won't move anymore. And it fells like it is getting jammed at that end too. I guess I could try moving the shaft of the act. all the way to one end and do the same with the potentiometer and see what that does.
Other than that I am at my wit'* end. really frustrated.
Suggestions????
I posted some pics so you can see what I'm doing.



he 2 square holes are for the dash vents.



mode door act. controls 2 doors.

You can move the doors easily and not sticking at all. They have to be VERY free.

yeah they are very free. no resistance at all. that'* why I'm stumped. I must be doing something wrong.
here'* what I do.
To let it reset I have unhooked the battery or took out the fuse for the HVAC then hooked back up or put fuse back in and then turned the key to run and it does it'* thing.
Also to clarify, when I said the blend door was spring loaded i was wrong, it moves one way and if i let it go it falls back down from gravity. in other words it moves up and then down. before when it was getting stuck it would move freely back and forth but it got stuck at the very end because it was hitting another door. I'll try and post a video of it and the act. being reset today.
It'* hot and humid here! And to make it worse, the A/C in my car just quit 5 days ago! I am going to post something about it in Oldsmobile.