car drains battery to point of having to jump start, so power draining, why?

there is nothing i can test, that you would be able to do, in a shop at home?

Volts meter batt ,should be 14.0 volts ,then while its running , turn everything on the heat ,stereo ,wipers see if holding charge at 14.0 volts

seemed like the wiper circuit caused a fluctuation in the meter between high 13 and low 14s charging volts, how to eliminate the switch from the motor, as the cause, would be next question, any ideas? thanks so much