2000 chevy blazer irratic fuel gauge and volt meter?

[Melba Toast]

my fuel guage gets irratic when fuel level gets to about 1/2 tank also my volt meter goes down to about 11 - 12 when i hit the brakes in traffic the alternator is new and i tested it but it is fine any ideas.

[uncle bob]

Check the dash electrical ground connections on the emergency brake pedal. They sometimes come loose and lose contact causing the gages to become erratic.