Course Title: Fundamentals of Automotive HVAC Systems

Duration: 2 Weeks (Monday – Friday).

“Automobile Heating, Ventilation, and Air Conditioning (HVAC)”. This outline balances theory with essential hands-on practice.

Target Audience: Aspiring or current auto technicians, mechanics seeking specialisation, or technical students.

Week 1: HVAC Principles, Components, and Basic Operation

• Day 1: Introduction, Safety, and Heating System Fundamentals
  • Morning (Theory):
    • Course overview and objectives.
    • Safety First: HVAC system pressures, refrigerant handling (R-134a, R-1234yf), chemical safety (oils, flush), electrical safety, proper use of Personal Protective Equipment (PPE – especially eye protection).
    • Basic principles of heat transfer (Conduction, Convection, Radiation).
    • Purpose of the automotive heating system.
    • Components: Heater core, heater control valve (if applicable), hoses, thermostat’s role.

• How engine coolant temperature affects heating.

Afternoon (Practical):

• Identifying heating system components on training vehicles/benches.
• Demonstration of safe handling procedures.
• Inspecting hoses and heater core connections for leaks.
• Basic thermostat testing concepts.

• Day 2: Ventilation System and Airflow Control
  • Morning (Theory):
    • Purpose of the ventilation system (fresh air vs. recirculation).
    • Components: Blower motor and fan, resistor block/module, cabin air filter, air ducts, mode doors, blend doors.
    • How airflow is directed (Defrost, Vent, Floor modes).
    • How temperature is controlled (mixing hot and cold air using the blend door).
    • Manual vs. Electronic controls (basic overview).
  • Afternoon (Practical):
    • Locating ventilation system components.
    • Inspecting and replacing a cabin air filter.
    • Testing blower motor operation at different speeds.
    • Testing blower motor resistor (manual systems).
    • Observing mode and blend door actuation (manual controls).
• Day 3: Introduction to Air Conditioning Principles & Refrigeration Cycle
  • Morning (Theory):
    • Purpose of the AC system (cooling and dehumidification).
    • Basic Thermodynamics: States of matter, heat absorption during evaporation, heat release during condensation, pressure-temperature relationship.
    • The Refrigeration Cycle: Explanation of the four main stages: Compression, Condensation, Expansion, Evaporation.
    • Role of refrigerant as the heat transfer medium.
  • Afternoon (Practical/Demo):
    • Using Pressure-Temperature charts for R-134a.
    • Demonstration of evaporation causing cooling (e.g., alcohol swab).
    • Tracing the basic flow of refrigerant on diagrams and training units.
• Day 4: AC System Components (High Side)
  • Morning (Theory):
    • Compressor: Types (fixed displacement, variable displacement), function (pressurizing refrigerant vapor), clutch operation.
    • Condenser: Function (rejecting heat, changing vapor to liquid), location, airflow importance.
    • Receiver/Drier (TXV Systems): Function (storing refrigerant, removing moisture/debris).
    • High-pressure lines.
  • Afternoon (Practical):
    • Identifying compressors, condensers, receiver/driers on vehicles.
    • Inspecting condenser fins for damage/blockage.
    • Demonstrating compressor clutch engagement/disengagement.
    • Locating high-side service port.
• Day 5: AC System Components (Low Side) & Refrigerants/Oils
  • Morning (Theory):
    • Expansion Device: Function (metering refrigerant flow, pressure drop), Types (Thermal Expansion Valve – TXV vs. Orifice Tube – OT).
    • Evaporator: Function (absorbing heat from cabin air, changing liquid to vapor), location, condensate drain.
    • Accumulator (Orifice Tube Systems): Function (storing refrigerant, removing moisture, preventing liquid slugging).
    • Low-pressure lines.
    • Refrigerants: R-134a vs. R-1234yf (properties, environmental impact, safety).
    • Refrigerant Oils: PAG vs. POE, viscosity, importance of using the correct type and amount.
  • Afternoon (Practical):
    • Identifying evaporators (location basics), expansion valves/orifice tubes, accumulators.
    • Locating low-side service port.
    • Demonstrating different refrigerant cylinders and oil types.
    • Discussing oil balancing during component replacement.

Week 2: Diagnostics, Service Procedures, and Climate Control

• Day 6: HVAC Electrical Controls & Basic Diagnostics
  • Morning (Theory):
    • Review of basic electrical circuits.
    • HVAC Control Panel inputs and outputs.
    • Compressor clutch control circuit.
    • Radiator/Condenser fan control circuits.
    • Pressure Switches/Sensors (High, Low, Binary, Trinary): Function and role in system protection and control.
    • Introduction to systematic diagnostics: Verify complaint, visual inspection, basic checks.
  • Afternoon (Practical):
    • Reading basic HVAC wiring diagrams.
    • Testing pressure switches (continuity checks).
    • Testing compressor clutch coil resistance and applying power (safely).
    • Using a multimeter to check fan motor circuits.
    • Introduction to Manifold Gauge Set: Connection and safety.
• Day 7: AC System Performance Testing & Leak Detection
  • Morning (Theory):
    • Connecting Manifold Gauges: Procedures and safety.
    • Reading Static vs. Operating Pressures (High and Low Side).
    • Factors affecting pressures (ambient temp, engine RPM, airflow).
    • Interpreting pressure readings for common issues (low charge, overcharge, restrictions, air in system).
    • Using thermometers to check vent temperature and condenser/evaporator temperature differential.
    • Common causes of refrigerant leaks.
  • Afternoon (Practical):
    • Connecting manifold gauges to vehicles.
    • Recording static and operating pressures under various conditions.
    • Measuring vent temperatures.
    • Leak Detection Methods: UV Dye and light, Electronic Leak Detectors, Soapy water (basics), Nitrogen pressure testing concepts.
    • Hands-on practice with UV light and electronic leak detectors.
• Day 8: AC Service Equipment and Procedures
  • Morning (Theory):
    • Recovery/Recycle/Recharge (RRR) Machine: Purpose and functions.
    • Refrigerant Recovery: Environmental regulations, importance of not venting.
    • System Evacuation (Vacuum): Purpose (removing air and moisture), procedure, importance of deep vacuum, vacuum decay testing.
    • Recharging the System: Methods (by weight vs. by pressure/volume – weight is preferred), adding refrigerant oil.
  • Afternoon (Practical/Demo):
    • Demonstration and supervised practice using an RRR machine:
      • Connecting hoses.
      • Performing refrigerant recovery.
      • Performing system evacuation (pulling a vacuum).
      • Recharging a system by weight.
• Day 9: Automatic Temperature Control (ATC) Systems
  • Morning (Theory):
    • Difference between Manual HVAC and ATC.
    • ATC Components: Control module, interior/exterior temperature sensors, sunload sensor, humidity sensor, blend/mode door actuators (motors), aspirator motors.
    • How ATC maintains desired temperature automatically.
    • Basic ATC diagnostics: Self-diagnostics codes, using a scan tool to view sensor data and command actuators.
  • Afternoon (Practical/Demo):
    • Identifying ATC-specific sensors and actuators on vehicles.
    • Demonstration of using a scan tool to access the HVAC module.
    • Viewing ATC sensor data stream.
    • Performing actuator tests using a scan tool (if available).
• Day 10: Common HVAC Problems, Troubleshooting Scenarios & Review
  • Morning (Theory):
    • Troubleshooting common complaints:
      • AC not cooling / blowing warm air.
      • Poor airflow from vents.
      • Noise from AC system (compressor, blower).
      • Intermittent cooling.
      • Water leaking into the cabin.
    • Integrating diagnostic steps: Combining visual checks, pressure readings, temperature measurements, leak detection, and electrical tests.
  • Afternoon (Review & Assessment):
    • Practical troubleshooting scenarios on training vehicles/benches.
    • Q&A session covering all topics.
    • Brief written or practical skills assessment.
    • Course feedback and closing.