A voltmeter set to read DC volts is used to test for galvanic activity and electrolysis. To check for excessive voltage caused by galvanic activity or electrolysis, perform the following steps.
STEP 1. Allow the engine to cool and then carefully remove the pressure cap from the radiator.
STEP 2. Set the voltmeter to DC volts and connect the black meter lead to a good engine ground.
STEP 3. Place the red meter lead into the coolant.
STEP 4. Read the meter. If the voltage is above 0.5 V, this indicates excessive galvanic activity. Normal readings should be less than 0.2 V (200 mV). Flush and refill the cooling system.
STEP 5. To test for excessive electrolysis, start the engine and turn on all electrical accessories, including the headlights on high beam.
STEP 6. Read the voltmeter. If the reading is higher than 0.5 V, check for improper body ground wires or connections. Normal readings should be less than 0.3 V (300 mV).

Next Steps towards ASE Certification

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