No Pin 3 Voltage on B and C VR

[Crank73]

I'm working through the B and C Voltage Regulator troubleshooting steps and have a voltage of 0 at pin 3. The guide states that pin 3 voltage should be within 0.2 V of Bat bus voltage and that a voltage of 0 will still allow the VR to work, but low voltage warning and over voltage protection will be lost. My alt field fuse is blowing after years of no issues. Voltages at other pins seem OK. I notice my system voltage while flying fluctuates quite a bit (14 to 15 v) while flying prior to blowing fuse. When fuse blows, low voltage warning light does come on so I'm confused about their statement reference losing low voltage warning with 0 volts at pin 3. This electrical problem also blew my starter fuse on last start attempt. Does this sound like a bad Regulator, lose wire or alternator issue. The guide doesn't mention what to check for with 0 v at pin 3.
Any tips would be appreciated.
Yanick