AC ripple Testing

[Mopar1973Man]

Depends. 

 

Full load ripple is going to be much higher typically the local NAPA passright right around 1.0 volts AC at full load 136 Amps.

 

Idling engine and no load with DVM you want to be 50mV AC or less. 

 

Output voltage is meaningless. It the ripple voltage that is critical here. 

[Mark Richart]

Where should you take the AC voltage reading, at the battery terminals or the alternator + stud to case? On mine the measurements at the alternator are much higher than at the battery.

[dave110]

At the alternator. Reason it's lower at the batteries is the batteries are acting like a filter and soaking up some of the AC.