Now time to switch to volts DC on your meter.

The bridge rectifier changes the AC volts to DC volts.

You could probe the black wire at BR3 with your black probe, but easier to connect to a common ground, like....
.....the ground braid.

Then use your red probe on the purple wires on BR3.

Check your reading.

I probably should also mention to be very carefull, when probing around with the power on.