I've had a voltage gauge in my car for about a year now, got it cheap to put in a hole where another gauge once was, it's tapped off the radio power (I know not a good place.)
It's been accurate. Noticed one day it was reading low, confirmed via hand held voltmeter alternator/battery voltage was around .5 volts higher. At same time I noticed my wbo2 gauge was a little off and didn't match AFR I saw from controller on laptop...
Ran a new + wire using relay/fuse from alt/battery distribution block, connected to wbo2 and gauges. Voltage gauge now reads correctly and wb02 gauge does as well..
Anyone else run into anything similar? Is this how re-wiring the entire car starts?