HVAC System Maintenance and Troubleshooting Procedures

Heating and Ventilation Troubleshooting

Insufficient heating: Check the heating tap or mixture hatch to ensure it is open. If the circuit has purgers, check their operation. Verify the operation of the thermostat and check the heating radiator.

Insufficient ventilation: Check the status of the cabin filter. Verify that the flaps are functioning normally. Check the air distribution and verify proper functioning.

Blower Motor Inspection

Blower: Check that pressing the switch turns on all speeds. Following the electrical schema, check the command switch. Listen for noises or squeaks caused by a lack of lubrication on the armature shaft and bearing supports. Check for vibrations caused by an imbalance of the turbine during its turn.

Refrigerant and Lubricant Specifications

Refrigerant fluid: Must have a low freezing point, high evaporation temperature, and low flammability. It should be non-oxidizing, non-corrosive, and easy to mix with lubricants while adapting to environmental standards.

Lubricant oil: Should resist foaming and not freeze. It must have the ability to mix with the refrigerant fluid and be purified and dehydrated to prevent ice formation within the circuit.

Filter Drier and Expansion Valve

Filter drier: Installed in systems with an expansion valve, it retains moisture and filters solid impurities. It accumulates refrigerant in a liquid state to prevent bubbles from occurring.

Expansion valve: The most frequent breakdowns occur when the expansion valve is stuck open or, on the contrary, stuck closed. To test, heat or cool the sensor bulb to observe a variation in pressure values. If this does not happen, it must be replaced. Whenever replacing the valve, the dehydrated filter must also be replaced.

Safety Standards and Procedures

• Prevent the refrigerant from coming into contact with the skin.
• If contact with the skin occurs, remove any clothing that was wet.
• If contact with eyes occurs, rinse thoroughly with water.
• Contact with flames or hot surfaces produces toxic gases.
• Gaseous refrigerant weighs more than air; there is a danger of asphyxiation.
• Refrigerant must not be released into the atmosphere.
• Welding or tinning should not be performed in air laden with refrigerant.
• During painting, do not exceed 80ºC.
• Do not smoke while handling liquid refrigerant.
• After creating a vacuum, do not leave the circuit open.

Fixed vs. Variable Volume Compressors

• Fixed (CVF): Uses a control plate; performance is constant; starts working with cyclic loops and stops.
• Variable (CVV): Uses a swash plate; performance varies from 4% to 100%; does not stop.

Malfunction Diagnosis and Performance Testing

Common Malfunctions

• Insufficient coolant
• Presence of air or moisture
• Compressor belt slips
• Internal faults or partial obstructions
• Stiff expansion valve

Performance Testing

• Set engine speed to 2000 RPM at maximum cold setting.
• The thermostat should measure an output temperature of 10ºC.
• Test with the bonnet closed at engine temperature regime.
• Inspect for leaks at unions, frost, or dirt on the condenser.

Compressor Failure Modes

• Galling or internal seizure
• Electric magnetic clutch failure
• Slipping of the drive belt
• Retention of the compressor