Electrical Systems, A/C & Maintenance
Battery testing, charging systems, CAN bus, DVOM, voltage drop, A/C refrigerants, oil service, and cooling systems.
- Interpret battery voltage and CCA testing results
- Explain alternator operation and parasitic draw testing
- Describe CAN bus communication and DVOM usage
- Identify A/C refrigerants, components, and service requirements
- Apply proper engine oil, coolant, and maintenance practices
Lección 1
Battery Testing & Charging System
Charging System Voltage
The typical charging system voltage is 13.5 to 14.5 volts with the engine running. This is the output from the alternator through the voltage regulator. Below 13.5V indicates undercharging; above 14.8V indicates overcharging - both damage the battery and electrical components.
Battery Voltage at Rest
The voltage that indicates a fully charged 12V battery at rest is 12.6 volts. A battery at 12.4V is approximately 75% charged, 12.2V is 50%, and 12.0V is 25%. Below 12.0V the battery is considered discharged and may not start the vehicle.
CCA Rating
A CCA rating (Cold Cranking Amps) for a battery measures the number of amps a battery can deliver at 0 F (-18 C) for 30 seconds while maintaining at least 7.2 volts. CCA is the primary specification for starting batteries - a higher CCA rating means better cold-weather starting ability. Battery testers compare actual CCA to the rated CCA to determine battery health.
Battery Testing Procedure
Before load testing a battery, ensure it is at least 75% charged (12.4V or higher). A discharged battery will fail a load test even if the battery itself is good. Charge first, then test.
A fully charged 12V battery reads 12.6V at rest. The charging system should produce 13.5-14.5V with the engine running. CCA measures starting power at 0 F - the higher the CCA, the better the cold-start ability.