voltage spike

[Cutty1]

what cause's voltage to spike up sorta speak my voltage needle moves up when engine warmed up, noticed it when the blower motor is on has (little transient's) every min or so.blower motor going out soon?, alternator maybe? my lights dim in an out too

 

[Blake442]

Take readings from a factory gauge with a grain of salt, as they're notoriously inaccurate.