tapping noise within dash when motor running ac

A rhythmical tapping noise sounds like the blower motor could be noisy, or maybe more likely there could be debris in the area of the fan that has caused it to get lodged in the blower wheel. Accessing the cabin air filter and checking for debris inside is the best first step towards diagnosis.

I know this reply is a little late, but it could be one of the mode or temperature door actuators. They have small motors and plastic gears that strip and can cause a tapping or clicking noise if they are trying to change position. If the tapping does not change in speed in relation to the speed of the blower motor itself, it's likely an actuator.