Hello. I have a 2000 Maxima with 181k miles. Heater just quit working. Fluid level is good and antifreeze is fresh. The blower motor works on all speeds and the air will work out of defost, dash and floor vents but the manual sliding temperature control has no affect on the air temperature. I've been under the dash on both sides of the car and see no movement on either side while sliding the control. I'm thinking maybe actuator bit not sure of the difference between blend and air mix. Any advice would be greatly appreciated. Thanks.

 

Blend door is stuck.