Three HVAC Diagnostic Scenarios

Situation #1: Lack of Cooling

Symptoms: Noise from AC compressor area

What should you do?

• Check condition of any airflow filter devices

• Performance test the A/C system

• Check the main A/C operating components

• Check the A/C pipe system components for mechanical security

• Check the A/C electrical system switching devices

Result with the Performance Test: Insufficient cold air from passenger compartment vents.

What would you do to IDENTYFY the problem?

• Perform an audible inspection of A/C pipes and hoses

• Perform visual inspection and listen the compressor with a stethoscope

• Perform a pressure test.

• Inspect magnetic clutch

• Perform an audible inspection of expansion valve

Result with the Pressure Test: System high and low side pressures considerably low.

What would you do RECTIFY the problem?

• Replace clutch coil or reset air gap

• Flush system, replace compressor and drier/accumulator

• Replace faulty motor/cable/linkage

• Replace TXV/FOT

• Recharge system as required. Check for leaks and repair as necessary

Situation #2: Lack of cooling.

Symptoms: Battery light on, overheating, or noise from engine compartment.

What would you do to VERIFY the complaint?

• Check the A/C electrical system switching devices.

• Check condition of any airflow filter devices.

• Check the main A/C operating components

• Check the A/C compressor drive devices

• Perform a visual inspection.

A Visual inspection was performed and the result is: Insufficient cold air from passenger compartment vents.

What you should do to IDENTIFY the problem?

• Check for adequate air flow from vents

• Visual inspection of A/C system

• Check in cabin mechanical flow control devices for operation

• Listen to compressor with stethoscope.

• Audible inspection of A/C pipes and hoses

Visual inspection of the A/C system: Broken A/C belt.

What should you do to RECTIFY the problem?

• Replace expansion (TX) valve

• Replace clutch coil or reset air gap

• Replace belt and inspect pulleys, tensioners, and driven components.

• Recharge system as required. Check for refrigerant leaks and repair as necessary

• Replace or re route pipes and retainers

Situation #3: Lack of cooling.

Symptom: Error message on climate display. Compressor cycles normally.

What you should do to VERIFY the concern?

• Performance test the A/C system

• Check the A/C compressor drive devices.

• Check the main A/C operating components.

• Check condition of any airflow filter devices

• Check the A/C pipe system components for mechanical security.

The result of a Performance Test (Verification) is: Insufficient cold air from passenger compartment vents. Air is actually heated.

What should you do to IDENTIFY the problem?

• Check that A/C compressor clutch engages

• Visual inspection and listen to compressor with stethoscope

• Check for adequate air flow from vents

• Visual inspection of A/C system

• System pressure check

After a System pressure test the result was: High side and Low side pressures are within specifications. Further inspection reveals the air blend door in heater box is stuck in the "hot" position.

What should you do to RECTIFY the problem?

• Replace belt and inspect pulleys, tensioners, and driven components

• Replace faulty motor/cable/linkage.

• Recharge system as required

• Replace AC pressure switch/sensor

• Flush A/C system, replace compressor, receiver/drier, and refrigerant

Situation #4: Unusual noise

Symptom: Poor performance of A/C system.

What should you do to CONFIRM the concern?

• Performance test the A/C system

• Check cabin mechanical devices

• Check condition of any airflow filter devices

• Check the A/C electrical system switching devices

• Check the A/C drive components