is it possible for my alternator to pass a test at AutoZone but my voltage regulator still be bad?

Question

'97 F150 5.4L V8
While vehicle is running my battery light is on, lights are dimmer, wipers slow, and battery gets drained. I had the alternator tested at Autozone they said it was OK. put it back in changed batteries same problem. would I be correct to say my voltage regulator is bad?

Answer 1

It's possible your voltage regulator is bad, but that should have showed up on the bench test. A lot of voltage regulators are built into the alternator, so if it is bad you will have to replace the alternator. You may have a loose or corroded battery connection or bad cable. I would remove and clean all the connections and terminals, and then have the battery and alternator retested while on the car.



Hope this helps and good luck

Answer 2

Alternator must charge between 13.5 - 14.0 volts with the car running and a *volt meter connected to the battery. 25 year old Fords were the last to have replaceable voltage regulators located outside the alternator in the engine compartment. If the charge back rate is lower than 13.5 volts your battery doesn't have a prayer of living more than 6 daytime hours when all the electrical systems are pulling high amperage loads. They all have voltage regulators inside the alternator now. You must sort out the charging system first before worrying about a new battery. Re-manufactured Auto Zone and Advance Auto starters and alternators are terrible. Short warranty period and filled with cheap off-shore parts.

Answer 3

Frankie hit it spot on in his diagnostic, I might add check all the vehicle grounds , cables, and connections for proper connections. and while you are at it make sure the connectors at the alternator are serviceable....good luck