anyone else with the same problem?

voltmeter (Circuit brand VMG 12V) is tapped to cigarette lighter socket. grounding point shared with other gages on the metal frame of dashboard.

problema ay nagflfluctuate ang reading from 12 - 14 volts and sometimes lower than 12. one time, nagzero reading. took readings with a digital tester also at the same point where voltmeter is tapped. ganun din nagffluctuate. pero battery reading is 13.74 - 14.4 volts kaso hindi ganon kagrabe fluctuation at the battery.

any inputs appreciated.