2006 pontiac montana sv6- alternator issue?

osguy98

occasionally at night- my lights dim and if I have the heat on, the fan would go quiet briefly. could this possibly be an alternator issue?

imidazol97

I've seen something like that happen when the engine cooling fans kicked on especially with AC on, when they may run at higher speed and higher amperage load on the battery and alternator. I'm not sure about the interior blower fan changing speeds. I'd suspect a battery or connection problem on the battery's leads at either end if the battery is good.

It may be related to how the alternator is controlled. I was leafing through my Cobalt's factory service manual a few months back and discovered the computer tells the alternator how to charge, at what voltage, based on which options are turned on. The options were the headlights, blower, etc.. So what you observe might just be the computer controlling the charging changing or resetting itself.