my 2000 mercury villager once u start it and disconnect the battery the van runs fine but if u leave the battery connected theres no power and doesn't shift right
This is strange! I'd have the battery tested, and most likely replace it anyway. The alternator must be working, but maybe the battery is shorted. The other possibility is that the alternator is weak, and can't charge the battery. Test the voltage when it's running, should be over 14 volts. Charge the battery overnight and see it it still happens. A good battery on charger all night should drop below 3 amps draw in the morning, or it's shorted.
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