Over the past few weeks the Chevy's volt guage would fluxuate (sp?) from normal (needle straight up the middle) to gradually going towards the left (bad[img]images/icons/crazy.gif[/img]). However the whole time I haven't noticed the battery being drained, haven't noticed any difference in the radio power, lights, etc.. just the guage going south.
I went to Advance Auto Parts and had them test my alternator and the guy said the tester showed "diode pattern good" whatever that means (Jason explanation please!). However past 2 days the guage has deep sixed into the left side of the guage. Still no noticeable change in starting (well maybe a little, but still starts on the first crank), radio, lights, etc. If its my guage how do I check it? What can I do to fix it?