It relates to the battery. Old battery (not sure it’s age), seemed to stop charging. I replaced it with a new one, assuming that was the problem, but one week later when I started the car for the 1st time since installing the new battery, the car would not even turn over, no lights would come on. The car was dead. Now I’m researching the matter and seem to come up with possible solutions: A particular fuse or fuse or alternator problem is draining the battery.
Are you telling us? Or asking? First you need to get a voltmeter. Check the battery voltage, it is new, it should be 12.6 or even more when charged. Start the car, check the voltage, is it 13.5 V to about 14.7 V? Then your alternator is OK. If it shows less than 13 V, the alternator has likely failed.
If the alternator checks OK, then you need a ammeter to measure how many amps the car draws when it is turned off. Disconnect the negative battery cable and put the ammeter between the cable and battery. Leave it connected for 2-3 minutes. You should see less than 1 amp draw and that should drop as the various computers start going to “sleep”.
After 3 minutes or so the current should stop dropping. What’s it read? More than about 0.05 amps on a simple car like this says you have a parasitic drain. Start pulling fuses until that drain goes away. Replace or fix whatever the device is that is causing it.
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You do realize that when you disconnect the battery, you force any offending module(s) to go to sleep?
Which means you’ll never find the offending module(s)?
Tester
Disconnected modules don’t sleep, they die. No current drain at all. That is of no use.
Once the battery is reconnected through the ammeter, the offending module won’t be disconnected. And I want to force it to “sleep” so that the keep alive current will drop down to its lowest level so the offending drain can be found. If the drain is an internal short, that drain will still be there and identifiable when the fuse is pulled.
On a more complicated car than this Neon, I’d check the voltage drop across each fuse with a very sensitive DVM.
Tester
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Good article for chasing confused F.R.E.D.s. Oddly enough that’s what we called them 40 years ago when they were first being created. Our acronym was a bit different. Freaking Ridiculous Electronic Device.