There is a small temp sensor in the car that adjusts the temp when in automatic mode. If this becomes dirty the interior of the car will not be at the correct temp.
Start by removing this small part of the dash. It only needs to come part way off. You will see 3 screws, these are torx screws.
You will then need to pop the lower part of the dash out of the way a little bit to get to a hidden screw. You only need to remove the right side screw.
Move the top piece out of the way and you will see the sensor. It gets covered with dust and will give false readings.
You can spray a little contact cleaner on it and then some canned air. You do not want to use a stiff brush on this as you could brakethe wire. Once clean, close the dash back up and put the screws back in place.