Attack of the coil killer!

You may have purchased a "bad" alternator or if external, have a bad voltage regulator. If you have a voltmeter, place it across the battery terminals and read the voltage BEFORE starting the engine. It should read 12.60 volts if at full charge or very close to it.

If you can get another coil, start the engine and run at about 1500 rpm (a fast idle). You don't really need a tach-just guess. Place the voltmeter across the terminals now and see what it reads. It should be higher than the previous reading but not above 14.5. (high 13's would be great). If any higher than 14.5 volts, you probably have a bad voltage regulator. This could result in almost everything electrical lights, wiper motor, radio, blower motor, etc., being damaged or burning up. Good luck.