I have noticed in the last month that the voltage meter on my 2002 Chevrolet Silverado fluctuates. Before, the needle always stayed well above 14 volts and never moved after the engine was started. Now the needle is fluctuating from just above 14 volts to just below 14 volts when it is idling and when operating at normal speeds if I turn on a signal light or change the blower fan speed or use any of the window, door locks, electric seats or heated seats controls the needle jumps. At night when the headlights are on if I brighten or dim the lights it really jumps. I have taken it to have the charging system and battery checked twice at 2 different auto parts stores. The first one the guy kind of acted like he didn't know what he was doing so two days later I went to a different store. Both times I got the same answer, that the battery was OK and the alternator was putting out 14.3 to 14.8 volts which is what they said it should be doing. Is there something that could be fixed before it breaks or is this normal.