Cranky,
I don't know about your car but my car uses;
8 amps for the msd box
8 amps for the lights
18 amps for my electric rad fan
4 amps for my electric fuel pump
10 amps for the wipers
12 amps for the heater/defroster
60 amps constant draw
Yes I have used them all at the same time, for hours at a time on our trip to Idaho. If your alternator can't put out enough to run these then your battery will discharge constantly.
Perry.
