Troubleshooting Dimmer Circuit
There are 2 possibilities for the coil and after reflection ( dim illumination... pun intended) I am changing my mind.  I think pin 1 &lt;>3 are shorted.    

To confirm ; purpose of coil as { gate trigger or surge current line filter}   


  if coil traces are in series with the  brown line voltage wire,
  ...  then it is a line filter in series with the LOAD
  ... then wick solder from Triac
   ... and carefully remove without hole damage from excessive soldering time.
  ... then retest Triac to confirm short circuit failure ( or not)    


( re-linked explanation of similar unit design except intead of Arduino this possible a ST uC. )