voltage gauge vibrates

[aknight_sa]

hi,

when i start my 2001 tahoe the voltage gauge starts shaking, even when i engage any electrical equipment such as opening a window, engage turn signal or lock or unlock doors the voltage drops like .2-.4 of a volt..

this is really annoying me.. what could be causing this?

 

[M3PO]

First, check alternator output with a meter and see if it has the same erratic movement. These trucks are known for the gauges going bad, so it could be the stepper motor moving the needle and not an actual fluctuation in voltage. I have a friend with a 2500 pickup truck and his oil pressure gauge is failing, his oil pressure is fine, the gauge is failing.
Anytime you turn on electrical items, you will have a slight drop in voltage, the greedier the item (rear defrost, heated seats) the more temporary drop you will notice. When I am pulling in my driveway and rolling up my windows at night, when the windows hit the top the headlights will flash for a second.