ok, so the problem is your charging system. the car is running off the battery right? like it'll die on him, correct? either it's a bad battery, or a bad alternator. a easy way to check if it's the alternator is to disconnect one of your battery posts( i prefer the negative) while the engine is on. i always did that if i had a problem, but people on this site would reccomend you take it to a shop............sorry i don't have a 90 accord so i can't tell you how to disconnect the alternator.