1991 jeep wrangler: alternator overcharging

Normally if you have a short in the circuitry it will pull down the voltage not increase it. I would check at the battery with a voltmeter and see what the indication is there. While at a normal idle if it is putting out more than 13.8 volts it is probably the voltage regulator. If the charging rate is in the acceptable range 12-14 volts at the battery the problem may lie in your gauge. Normally if you have a short in the circuitry it will pull down the voltage not increase it. I would check at the battery with a voltmeter and see what the indication is there. While at a normal idle if it is putting out more than 13.8 volts it is probably the voltage regulator. If the charging rate is in the acceptable range 12-14 volts at the battery the problem may lie in your gauge.

I know it's 13 years later but for any future people who come across this information Anonymous is wrong about the voltage regulator. Since 1989 all Chrysler/Dodge/Jeep vehicles the voltage is regulated by the PCM, there is no regulator inside the alternator so changing the alternator will not correct this particular issue. You either need to do an external regulator bypass or replace the PCM. I know it's 13 years later but for any future people who come across this information Anonymous is wrong about the voltage regulator. Since 1989 all Chrysler/Dodge/Jeep vehicles the voltage is regulated by the PCM, there is no regulator inside the alternator so changing the alternator will not correct this particular issue. You either need to do an external regulator bypass or replace the PCM.