Visual inspection: check belt condition/tension, wiring/connector condition, and signs of overheating or corrosion
Battery baseline: measure battery voltage with engine off
Start engine: measure charging voltage at battery terminals with engine idling
Increase RPM: measure charging voltage at 1500–2500 RPM
Voltage target check: confirm charging voltage is within vehicle spec (commonly about 13.8–14.7 V)
Load test: turn on headlights, blower, rear defroster; recheck charging voltage
Voltage drop check: if voltage drops significantly under load, suspect alternator, regulator, or wiring
Ground/connection check: inspect and clean battery terminals and alternator ground connection
Output current test (if available): use a clamp meter or alternator tester to verify output amperage
Ripple test (if available): measure AC ripple voltage; high ripple indicates alternator/rectifier issues
Diode test (if available): perform alternator diode test; failed diodes indicate alternator failure
Regulator test (if applicable): verify regulator function via alternator tester or voltage behavior vs RPM
Belt slip check: look for belt glazing/cracks and verify belt isn’t slipping under load
If equipped: check charging system warning lamp behavior and scan for alternator-related DTCs
Final verification: repeat measurements after cleaning connections or replacing suspect components