98 XC - While driving at night, I can notice the headlights and the dash lights dim lightly and then come back to bright. I would say it is about a 5-10% decrease. Barely just enough to notice it. It is for just a brief split second and then back to bright. Not consistent. They can blink for about 15-30 seconds dim / bright and then stop for ten minutes. There appears to be no engine changes, no change in idle. No warning lights. It can happen while idle or driving 50 mph. Flat or rough road. Does not appear to be a loose bulb because they all dim. Any ideas. I plan to look at it today and want to get some feedback on what to look for. Alternator going bad? How to check? I believe my wife said she noticed this awhile ago. Thanks