I have a 1990 Mustang 5.0 with a 3G alternator. Yesterday I went to hook up a new battery and accidentally connected the battery wrong. There was smoke by the starter solenoid it was only connected for about 2 seconds. Hooked up the car battery correctly and the car started right up however I noticed the battery light was flashing on the dash. It flashes on and off but mostly stays on. I got my voltmeter and the alternator is charging between 16.7 to 17.8 volts which is much too high of a charging voltage. I shut the car off right away. Could I have fried the regulator or possibly blown the 14 gauge green fusible link at the starter solenoid? The fusible link is semi hard and you can see clear glue like stuff hardened around it...but if the fusible link was blown wouldn't the alternator not charge at all? Any help is much appreciated I would really like to take the car out soon.
Take the alternator and get it tested, you probably fried it. Replace the suspect fuse link and inspect all the cables and wires associated with the starting/charging system that would be live with the key off. replace anything remotely suspect to damage.