SPECIFICATION Operating Environment: temperature: 0°C ~ 40°C relative humidity: < 75% Storage Environment: temperature: -10°C~ 50°C relative humidity: < 85% Size: 102×46×16mm ( main body only ) Weight: About 73g ( GK503 only ) About 43g ( GK503A only ) Charger Check While charging a 12V battery with a battery charger, connect the "Battery Check" to the battery terminals (red to positive & black to negative). When the red light against "Charger Check" is lit, the charging is complete. Alternator Check To check the charging circuit of a 12V vehicle battery, connect the red clip (or red probe) of the tester to the positive teminal of the vehicle battery, and connect the black clip of the tester to the negative terminal of vehicle battery. Accelerate your engine to 2000 rpm. If the red light against "Alternator Check" is lit, the charging circuit is well-worked. Cranking Check To check the cranking ability of vehicle's starter motor, connect the red clip (or red probe) of the tester to positive terminal of the vehicle battery, and connect the black clip of the tester to the negative terminal of the vehicle battery. The red light against "Cranking Check" should remain lit when the sterter motor operates. WARNING 1. Before use, inspect the tester. Do not use the tester if it is damaged. 2. Before use, verify the tester's operation by testing a known 12V battery. 3. Always follow the relevant instructions and procedures indicated in the vehicle's users manual and service manual. 4. Do not use the tester where explosive gas, vapor, or dust is present. 5. To avoid personal injury and tester damage, do not touch any moving or turning object of vehicle. Do not touch any high-temperature object with hand or skin. 6. To avoid electric shock, don't touch any naked conductor with hand or skin. 7. Use caution when working with voltage above 30V ac rms, 42V peak, or 60V dc. Such voltages pose a shock hazard.