Battery warning light stays on or comes on while driving
Headlights dim, flicker, or get brighter and dimmer with engine speed
Battery keeps dying or needs frequent jump-starts
Electrical accessories work poorly or intermittently
Engine cranks slowly or struggles to start
Burning smell from the engine bay
Whining, grinding, or squealing noise near the alternator
Voltage test shows about 13.5 to 14.5 volts with engine running; lower or unstable readings can indicate a bad alternator
Battery test is good, but the battery still drains while driving
Engine stalls after the battery loses charge
Corroded, loose, or damaged alternator wiring or belt
Alternator belt is loose, worn, or slipping
Dashboard lights behave erratically
Power windows, radio, or air conditioning act weak or fail
Alternator case is hot to the touch after normal driving