Sounds like igniter is firing.......which means DC is still going to circuit board when it should not be there.
Turning local ON/OFF---CB OFF drops the DC out.
Only way DC can get to Circuit Board is via Sail Switch and limit switch circuit.
Limit switch is always closed (unless high temp)
Sail switch should only close when fan runs and open when fan stops.
Stuck sail switch.
It is right by that on/off--cb
Small micro switch with a 'paddle' that still into fan blower chamber
Next time you hear the clicking...check if paddle is still 'up' (switch closed)
Move paddle down (switch open) should stop clicking noise
IF so........then replace sail switch (can try cleaning)
