Sorry for posting this here, but there is no Geo newsgroup.
My Geo Metro has a problem. It seems there is an intermittent drain on the battery when the car is off. The battery is two years old and the alternator is new.
It will be fine for weeks, then one morning the battery will be dead after working fine the day before. The dome light is not on, nothing in the car is turned on that I can tell; but something must be draining the battery.
I measured the voltage between the posts yesterday and it was 12.5 volts, should be over 13 so I suspected the draining thing was happening. I popped off the ground cable and measured the voltage between the negative post and the ground cable, and it was 11.5 volts. Checked between the posts and that was still 12.5 volts. Why would I measure one volt less going through the cable? Does that mean there is something using power and thereby causing the voltage to be less when measured that way?