- Make sure the engine is OFF, and turn the headlights on for 15-20 seconds to remove any surface charge from the battery.
- Using a DVOM set to volts DC, probe across the battery terminals.
- Measure the battery voltage.
- Write down the voltage reading and proceed to the next test.
- With the engine running, turn on the blower motor and the high beams (or other electrical accessories to place a load on the charging system).
- Increase and hold engine speed to 2000 rpm.
- Measure the voltage reading at the battery.
- The voltage should increase at least 0.5 volts from the voltage test. If the voltage does not meet specifications, the charging system is malfunctioning.
NOTE: Faulty wiring and other problems can cause the charging system to malfunction. Further testing, which is not covered by this book, will reveal the exact component failure. When all affected wires and components have been confirmed in good working order, under and overcharging is caused by a defective generator or internal regulator. Replacement of these components will then repair the condition.
- Connect a tachometer to the engine.
CAUTION
Place the transmission in P (Park), set the emergency brake and chock the rear wheels to prevent vehicle movement.
- Turn off all electrical loads (radio, blower motor, wipers, etc.).
NOTE: it is a good practice to turn off all electrical accessories prior to shutting off the engine.
- Start the engine and increase engine speed to 1500 rpm.
- Measure the voltage reading at the battery with the engine holding a steady 1500 rpm. Voltage should have raised at least 0.5 volts, but no more than 2.5 volts.
- If the voltage does not go up more than 0.5 volts, the generator is not charging. If the voltage goes up more than 2.5 volts, the generator is overcharging.
NOTE: Faulty wiring and other problems can cause the charging system to malfunction. Further testing, which is not covered by this book, will reveal the exact component failure. When all affected wires and components have been confirmed in good working order, under and overcharging is caused by a defective generator or internal regulator. Replacement of these components will then repair the condition.
