[DanEC]

With a 12.64 battery voltage, parking lights on, key off:

Driver side tail light 12.24 volts

Pass side tail light 12.21 volts.

Interestingly I was picking up .2 volts at the turn signal lead at the lights.

How am I supposed to check voltage drop across the trailer relay? When flashing the voltage is jumping up and down of course. I thought I might get something from the red wire on the car side from the brake switch by pushing on the brake pedal but it was only a few volts. I also noticed the same .2 volts across the relay with the parking lights turned on.