66 Valiant Starting Aggravation
You can't just wish it will work, you have to systematically CHECK some things.
1...Make REALLY sure all lamps are OFF. Does it have an underhood or trunk lamp? glovebox?
2...Shut everything down, unhook the ground, and connect your 12V test lamp "in dim lighting" between the battery post and ground. Does it light? Look close? Does it light DIMLY?
If so, you have a drain.
3...If this shows nothing, get your multimeter. Set it up for the highest amperage reading the meter is capable of and replace the test lamp with the meter. Any reading? Decrease the meter range. Any reading?
If you don't know how to set up your meter, post a good clear photo of the meter, or at least the brand and model of the multimeter. We can step you through that.
4...If the tests above don't show anything, make CERTAIN the system is charging. You still have an ammeter? You understand how they work?
Get the engine warmed up, and the battery "normalized" (charged up after starting). Normally, the ammeter should be CENTERED in this condition. run the engine at a fast idle with all accessories OFF. Check the running battery voltage right at the battery. It should run about 13.8--14.2, not below 13.5, nor above 14.5.
Now turn on accessories, headlights, heater, etc. Again, with engine running "fast" recheck the voltage. It should hold steady at AT LEAST 13.5 and hopefully 13.8--14.2
5...If these checks show OK, remove the battery and have it "load tested."