Don't trust that old gauge to be completely accurate. Gauges do break or misread things as they get older so the first thing you need to do is to get a Voltmeter and meaure the voltage across the battery terminals. There you will get the CORRECT voltage reading that the car is putting out. Compare the voltmeter reading with what the gauge is telling you and I would not be suprised if the guage is showing a higher reading then the volt meter. If so then get another gauge from the boneyard to replace the faulty one. I have a volts gauge on my 264GL that reads in the red area sometimes. When I tap the glass of the gauge the needle dropes down to the middle area. When I check the voltage across the battery I read 14.5 volts even though the gauge is telling me 16V's. Ah, the games me an my 79 264GL play... Good Luck!!!

Sincerely,
--
Julio Meza

1979 264GL B27F 126K --> BW55->M46, CLS, IPD Sway, 81+ Dash, Gauges, Flat Hood & E-Codes

1979 262C B27F 161K --> Restoration Project

1984 245DL 216K --> Wifemobile / Sport Wagon