I just put in an alternator in my car but my battery boils. This has happened to two batteries. What could be the problem
Bad regulator is allowing the batteries to overcharge. I think the regulator is inside the alternator. That means the alternator you installed is likely bad.
Check the voltage with the car running. If it is over 14.6 volts, that will boil the battery.
Voltage ok, but I found that the cap on the battery wasn’t letting air out, so the battery was boiling. Put different cap on and ran the car at idle for an hour and lifted the cap and no water or air discharging. Is this a problem with Interstate batteries, do you know?