Think like a diagnostic technician
Successful diagnosis goes beyond choosing a component. In each case, gather required observations, identify the supported fault in the simulated scenario, select the correct authorized action, and choose a verification method.
Finish seven cases and score at least 10/12 on The Challenger. Lessons can be marked complete as you study.
Virtual completion does not verify real shop competence, refrigerant-handling credentials, or qualification to work on high-voltage systems.
From complaint to test plan
A customer complaint is a starting point, not a parts order. Reproduce the symptom safely, establish operating conditions, identify the relevant system path, and compare command, permission, and actual response. Separate airflow, air temperature, coolant heat delivery, refrigerant-side performance, and electronic control faults.
Ambient load, initial cabin state, blower speed, mode, temperature request, recirculation and symptom timing.
State what each measurement would confirm or rule out; do not treat a single vent temperature as refrigerant charge proof.
Look for the observation with the greatest diagnostic value before choosing a part.
Connect the five HVAC paths
The full system includes (1) cabin air path, (2) refrigerant heat-transfer path, (3) engine coolant or electric heat path, (4) electrical power and actuator path, and (5) networked control and permission path. Multiple paths can produce a similar customer complaint.
Inlet → filter → blower → evaporator/heater air path → blend/mode doors → outlets.
On conventional A/C, refrigerant transports heat between evaporator and condenser; system designs vary.
A request must pass protection/permission logic before an actuator operates. Actual mechanical response must still be verified.
Verify repair, not just an output
A credible repair closes the loop: baseline, measured diagnosis, authorized correction, repeatable verification, and documentation. Repeat the original conditions when safe and record objective before/after results.
Write down the complaint, exact setpoints, ambient conditions, response and measured evidence.
Repair only the fault actually confirmed by approved tests and service information.
Repeat the original test and check for remaining faults, safety concerns or related symptoms.
Know your service boundary
This capstone is a conceptual and low-risk diagnostic exercise. Refrigerant recovery, handling and charging require applicable credentials, approved equipment and procedures. High-voltage HVAC equipment, energized testing, cooling-system pressure and moving fans require vehicle-specific safeguards and qualified supervision.
Never vent refrigerant, open a charged circuit, guess charge from a single pressure or add refrigerant blindly.
Do not probe, bypass interlocks, open HV components or treat an A/C request as permission to energize them.
Beware of hot pressurized coolant, rotating fans, belts, and unexpected automatic starting. Use specified isolation and PPE.
Seven customers. Seven evidence-led repairs.
Choose a case, reveal observations, then submit a supported diagnosis, authorized action and matched verification. Each case is intentionally simplified. A real vehicle may have several competing faults; confirm against model-specific service information.
Select your first case
Choose a customer complaint above to begin.
Collect observations 0 gathered
Completed cases on this device: 0 / 7. A case is complete only when the correct three-part plan is submitted after collecting required evidence.
The Challenger · Final Check
Answer all 12 questions. A score of 10/12 meets this virtual target; answers include explanations for review. You may retry without losing your highest score.
Practical challenge · Eight shop tasks
Use these tasks with a qualified instructor and an approved vehicle or trainer. Checkboxes record your preparation only; they are not proof of instructor verification or qualification.
Your capstone status
Complete the seven cases and earn 10/12 on the assessment to meet the virtual target.
This standalone unit stores its own progress in this browser on this device. It does not sync across units or student accounts.
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