12.02 volts is
3/4 dead. No wonder you're having starter problems.
CHARGE THE BATTERY before doing anything else. Ideally, you'd charge and then load-test that battery.
When I bought the battery, it had 12.8 volts. About a week ago I checked again and it was 12.20, and tonight it's 12.02. The engine will do this regardless of the ambient temperature, although the cold doesn't help right now. I have the battery disconnected while I'm at work so nothing on the truck will affect the charge.
Checking resistance on a heavy cable such as the main battery cables is one step away from totally useless.
ONE good strand in the battery cable will give you a low resistance reading, but the cable won't conduct the amperage needed to start the vehicle.
Battery cables, and the alternator output cable are best tested by checking for
voltage drop when the starter is cranking, or when the alternator is full-fielded (max output at fast idle.)
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