My battery hand on my 1993 roadmaster is on 18 why?

I'm assuming that refers to the voltage. 18 is kinda high, but still okay- 'the car won't start' meaning there is no fire and spark, or it's not turning? Have your battery connections been hosed clean of any corrosion, and the connections wirebrushed clean? this is key to a healthy charging system.

With a 10 dollar volt meter on car battery and motor running should see between 13.4 to 14.4 volts. When over 14.4 the voltage regulator is bad.