At what voltage on AR3B pin 6 should I expect AR3B's output (pin 6) to go low? I'm getting almost 6V on pin 3 before the output goes low. Changing AR3 does not fix it.
According to the schematic there is 160 uA flowing through the opto when AR3B pin 7 goes low. We can't know what the opto is doing, but that's almost certainly not enough.
So you want to know of the input is above or below 110 volts. Did the math in my head so it might be wrong.
I connected up the supply(s).
There should be a 0.1uF cap across the 10V. (some cap)
1k resistor is for about 9mA in the opto isolator.