|
Your battery is bad. That's the only way to get 13.8 off the alternator and less at the battery...
Under load, your battery isn't putting out the voltage it should...
Get the battery replaced...
A battery can read "fully charged" at >12v off a charger, and be dead. the moment it sees a load.. A new battery, with NO FUNCTIONAL ALTERNATOR would still read >12v while the car is running...
|