[yco]

if you re 100% sure of the window mechanism has no problem or the dirt among those parts that seals the window.. well first of all if you re not planning any road trip pretty soon, i d not take any action yet after seeing window rolling oddness.. looks like an alternator problem more likely though..

voltage should be 13 and above whilst engine is running thats for sure.. there are ways to check the alternator and battery.. but it should be under on more exaggerated circumstances like no start up.. like unplugging the the positive cable on the battery while engine is running.. if engine dies its an alternator problem if not battery.. in your case since you can see the voltage with that gauge, voltage should go up when you rev the engine.. if it doesnt go up or goes up less than 0.1v its an alternator problem for sure..