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WorksheetsThree HVAC Diagnostic Scenarios
Total questions: 12
Worksheet time: 24mins
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
After a Performance test the tech find that there is a hissing noise from heater box area.
What should you do IDENTIFY the problem?
Perform audible inspection of A/C pipes and hoses
Perform system high side and low side pressure check
Perform visual inspection and listen to compressor with stethoscope
Perform audible inspection of expansion valve
Perform visual inspection of A/C system
After an audible inspection of the expansion valve, it was sticking/faulty making excessive hissing noise.
What should you do to RECTIFY the problem?
Replace damaged/blocked component(s); evacuate system and recharge with the proper amount of refrigerant
Replace faulty motor/cable/linkage
Replace or re route pipes and retainers
Recharge system as required
Replace expansion (TX) valve
