2002 Yukon GMC- Blend actuator quit working after battery was replaced. Will now work only on defrost mode. Have tried the reset options suggested by others including disconnecting battery and removing HVAC fuse under hood to let it reset. I don't think the actuator could have gone bad by just changing battery. What else can I do?

https://www.google.com/search?q=2002+gmc+yukon+denali+xl+blend+door+actuator+location

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You forgot to say what kind of vehicle this is but if you changed the blend door actuator you changed the wrong one you need to change the mode door actuator. I hope this helps. Take care.

I really don't think arcing the battery as you say did anything .The mode door actuator needs to be replaced . The gears are striped inside ,common problem .
https://www.youtube.com/watch?v=vWBGKfl7k24

Right side or left ? Electronic Automatic Temperature Control or manual ? Temperature or mode door ?
Temperature Blend Door Actuator - LH Removal and Installation
NOTE: It is not required to install the new LH temperature blend door linkage parts included in the LH temperature blend door actuator service part kit if only the temperature blend door actuator requires replacement and the linkage parts are not broken or binding.
LH temperature blend door actuator and linkage

1. Remove the 2 lower steering column opening cover bolts.

1. Detach the lower steering column opening cover.

1. Disconnect the in-vehicle temperature sensor aspirator hose and electrical connector.

1. Position the instrument panel wire harness away from the LH temperature blend door actuator.

1. Remove the 3 LH temperature blend door actuator screws.

1. Disconnect the LH temperature blend door actuator electrical connector.

1. Remove the LH temperature blend door actuator.

1. Manually operate, and inspect the LH temperature blend door linkage for incorrect placement, binding or damage.

Temperature Blend Door Actuator - RH, Dual-Zone EATC Removal and Installation
NOTE: It is not required to install the new RH temperature blend door linkage parts included in the RH temperature blend door actuator service part kit if only the temperature blend door actuator requires replacement and the linkage parts are not broken or binding.
RH temperature blend door actuator and linkage

1. Disconnect the glove compartment damper from the glove compartment.

1. Remove the glove compartment.

1. Remove the RH lower instrument panel insulator.

1. Remove the RH lower floor console trim panel.

1. Remove the 3 RH temperature blend door actuator screws.

1. Disconnect the RH temperature blend door actuator electrical connector.

1. Remove the RH temperature blend door actuator.

1. Manually operate, and inspect the RH temperature blend door linkage for incorrect placement, binding or damage.
2. Mode Door Actuator - Defrost/Panel/Floor Door
3. Removal and Installation
   NOTE: The defrost/panel/floor mode door actuator can be accessed from below the driver side of the instrument panel.
   NOTE: It is not required to install the new defrost/panel/floor mode door linkage parts included in the defrost/panel/floor mode door actuator service part kit if only the mode door actuator requires replacement and the linkage parts are not broken or binding.
   Mode door actuator and linkage
   1. Remove the 3 defrost/panel/floor mode door actuator screws.
   1. Disconnect the defrost/panel/floor mode door actuator electrical connector.
   1. Remove the defrost/panel/floor mode door actuator.
   1. Manually operate, and inspect the defrost/panel/floor mode door linkage for incorrect placement or damage.
   Mode door actuator linkage only
   
   1. Remove the mode door linkage.
      1. Depress the tab and remove the panel door lever.
      1. Remove the floor/defrost door intermediate lever screw and floor/defrost door intermediate lever.
      1. Pull straight outward to remove the floor/defrost door lever.
   Mode door actuator and linkage
   
   1. NOTE: When installing the mode door actuator, make sure that the panel door lever and floor/defrost intermediate lever are correctly aligned with the mode door actuator cam.
      To install, reverse the removal procedure.

According to the book, I'm showing a mode actuator and a blend door actuator next to it. Some models use cables and some use small electric motors to move the doors.
Are you sure you are working on the right door ?

Actually you can repair them I did mine it was switching to hot on its own I would have to shut the car off and back on to get cold back but I took the actuator off took it apart and the factory greased the thing so much there was a glob of grease that dropped down on the circuit board cleaned it off put it back together and it worked just fine going on the second year still no problem

Could be the HVAC control processor is malfunctioning.Wtihout testing that would just be a guess .
2003 Tahoe No Rear Heat Fix Suburban Yukon XL Repair

It's possible the HVAC needs to recalibrate itself, try the following;
With key on, set all HVAC controls and switches to their OFF or CCW positions. Turn key off, disconnect battery for a few minutes, then reconnect battery. Turn key on, but do not touch any HVAC controls for about 2 - 3 minutes. After that, see if the vents and all other functions work. If this does not solve the problem, either the mode control actuator(s) or mode door(s) are stuck or defective.

If you are getting heat only on the pass. side then I believe the blend door has failed. Dodge has a fix and the job is not easy as almost the whole dash needs to come out in order to get to the heater box and the door. I have read that a simple flush of the heater core will cure it, But that diidn't work for me. I think because dual climate control was an option the door is set up to control the two sides of the cab. When it fails only the pass. side gets heat.

Unfortunatly you do have to remove the dash to access any of the blend door or fresh air door actuators
here is a step by step proceedure this takes aprox 5 hrs in a shop so plan on a weekend at home good luck

FLOOR - DEFROST DOOR ACTUATOR

REMOVAL

WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE, THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE BEFORE PERFORMING FURTHER DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN AN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.

Disconnect and isolate the battery negative cable.
Remove the instrument panel assembly from the vehicle.



Fig. HVAC housing, dual zone shown (single zone similar)-nut (1), passenger blend door actuator (2), nut (3), inlet baffle (4), recirc door actuator (5), recirc air door (6), driver side blend door actuator (7), HVAC housing (8), bolt (9), defroster door actuator (10), mode door actuator (11)

Remove the electrical connector from the actuator.
Remove the mounting screws from the actuator.
Remove the actuator from the HVAC housing.

INSTALLATION
Install the floor-defrost door actuator to the HVAC assembly.
Install the mounting screws and tighten to 2.2 Nm (20 in. lbs.) .
Install the actuator electrical connector.
Install the instrument panel assembly into the vehicle.
Connect the battery negative cable.

I suggest check (or replace if is necessary), the blend door it is a huge project you have to remove the dash board. There is a repair kit available either way it is a 8 hr shop time project.

Hope helps.

This is probably due to a faulty blend door or blend door actuator. The blend door is a device inside the dash that directs the air flow to the desired vent. Sometimes they will fail, but usually is an actuator. Unfortunately, you will have to remove the dash to see if this is the problem. If you have never removed the dash on a Yukon, you are in for a very big job. Here is also some good information