Yes, if it is allowing the battery to be overcharged, it will ruin the battery.
Yes, it can over or undercharge the battery. If i is overcharging it can ruin the battery. If it is under charging the battery will just run down. Check the voltage at the battery with the engine running. You should read around 13.5 to 15.5 volts.
Alternator is defective and is not keeping the battery charged. Or, you have a light or relay that is on pulling power from the battery. Start the engine and check the voltage at the battery with a digital volt meter. You should have 13.5 to 15.5 volts if the alternator is good.
No, that will have no effect on the battery.
If your battery is dead,,,nothing should be flashing. There is no voltage to anything.
check battery if it has water and check the starter
Dead cell in the battery or the ignition or lights were left on.
This will not work on many OBD (compterized) cars. The engine will die shortly after disconnecting the battery cable. The computer must be power by the battery.
test the voltage on the battery first, then on the alternator. If its good then it could just be the diode in the alternator. I would suggest you replace it becuase eventually your alternator will die and the battery will not get charged leaving you stranded somewhere. It is possible to just be a battery but you wont know unless you have the battery tested. check the voltage on the battery and the alternator before you do anything else.
The same thing happened to me in my 1984 Mercury (I know, not the same), But it turned out to be the voltage regulator. Some older alternaters dont have internal voltage regulators.
You will destroy the voltage regulator if you unplug the battery while it is running, then you will have to replace the alternator anyways.
it's already well dead if it is corroding
Check your battery voltage. It should be reading over 12 volts while cranking. Todays batterys will not even take a jump when they die... Are the battery cables corroded? Check to see if the ground cable is secure to the block