another stupid electrical question, what is right/normal/bad Options

[timofly]

74 2.0 FI with console voltage gauge, shows 13+ volts running with no lights on. Turning on parking lights or stepping on the brake drops it to about 12.2. Turning on headlights drops it further to just below 12. Fog lights have no effect (they are working) but turn signals will drop it to 11 with headlights on. Brakes with headlights on also drops it to 11 volts. Battery (Red Top) shows 12.5 volts with engine off after a good run.

Before someone says: "Did you read the threads here on this?" Yes, I have, and the same conditions draw responses ranging from "that's normal" to "your regulator/aternator/phisoginator is about to fail", so they leave me right where I started.

I have cleaned the grounds in the front fenders right by the headlight motors, with no effect.

So, three dumb questions:

1. what's the best way to check the voltage being sent to the battery
2. where is the ground connection to the body for the tailights,
3. am I worrying about nothing?

Happy Thanksgiving to all and thanks for any advice.