In-Vehicle Testing

Never start the engine while carrying out this test procedure, as the alternator could be permanently damaged.
1. If lamp fails to light up when ignition is switched on, ground D terminal on alternator while ignition is still switched on.
2. If lamp lights up, electrical system is satisfactory and alternator is faulty.
3. Connect voltmeter across battery terminals.
4. Run engine at medium-high RPM for several minutes and read voltmeter. Reading should be 13.5-14 volts.
5. Connect ammeter to alternator output circuit (B) or use clip-on ammeter.
6. Run engine at about 2500 RPM.
7. Apply maximum electrical load to alternator either by connecting special carbon film resistor to it or by switching on all of vehicle's electrical equipment.
8. Read ammeter. Reading should be 45-90 amps for 2.3L engine and 60-120 amps for 2.5L engine.
9. Connect voltmeter across battery positive terminal and alternator B terminal.
10. Run engine at 2500 RPM and apply electrical load to alternator by switching on all lights.
11. Read instrument, then connect voltmeter across battery negative terminal and alternator B- terminal (ground).
12. Run engine at 2500 RPM and apply electrical load again. Read instrument.
13. Readings taken above should not exceed 0.5 volts. If higher reading is obtained, check relevant circuit for shorting or continuity.