CAR Troubleshooting & Diagnostics 3 — Questions and Answers
Question 1: A microwave oven turns on but does not heat food. Which component is MOST likely faulty?
- Turntable motor
- Magnetron tube (Correct answer)
- Control panel touchpad
- Interior lamp socket
Correct answer: Magnetron tube
The magnetron generates the microwave energy that heats food; if it fails, the oven operates normally except no heating occurs.
Question 2: A refrigerator makes a clicking noise every few minutes but the compressor never starts. Which component should be tested?
- Evaporator fan motor
- Start relay or overload protector (Correct answer)
- Defrost timer
- Ice maker module
Correct answer: Start relay or overload protector
A faulty start relay or overload protector repeatedly attempts and fails to start the compressor, producing a clicking sound each cycle.
Question 3: During recycling intake, an oven's broil element works but the bake element does not. What is the FIRST diagnostic step?
- Replace the bake element immediately
- Check for continuity in the bake element with a multimeter (Correct answer)
- Test the oven temperature sensor
- Inspect the convection fan motor
Correct answer: Check for continuity in the bake element with a multimeter
Testing continuity in the bake element confirms whether the element is open-circuited before condemning or replacing it.
Question 4: A front-load washer displays an E3 or UE error code during spin. What does this typically indicate?
- Water supply pressure is too low
- Drain pump is blocked
- Load is unbalanced in the drum (Correct answer)
- Temperature sensor has failed
Correct answer: Load is unbalanced in the drum
An unbalanced load error (E3/UE) occurs when the drum detects uneven weight distribution that could damage the machine during high-speed spin.
Question 5: Which symptom MOST suggests a faulty defrost heater in a frost-free refrigerator?
- Compressor runs but never shuts off
- Excessive frost buildup on evaporator coils (Correct answer)
- Water pooling under the crisper drawer
- Noisy condenser fan blade
Correct answer: Excessive frost buildup on evaporator coils
A failed defrost heater cannot melt accumulated frost from the evaporator coils, leading to heavy frost buildup that restricts airflow and cooling.
Question 6: When diagnosing an electric range with one burner that heats weakly, what is the MOST likely cause?
- Faulty main circuit breaker
- One leg of the 240V supply is missing
- Defective oven control board
- Worn surface element socket contacts (Correct answer)
Correct answer: Worn surface element socket contacts
Worn or corroded socket contacts create resistance in the circuit, reducing current flow to the surface element and causing weak heating.
Question 7: A technician uses a manifold gauge set on a refrigeration unit and finds suction pressure is very low with discharge pressure normal. What does this indicate?
- Overcharge of refrigerant
- Restriction in the liquid line or filter-drier (Correct answer)
- Faulty condenser fan motor
- Compressor valve leak
Correct answer: Restriction in the liquid line or filter-drier
A restriction in the liquid line or clogged filter-drier starves the evaporator of refrigerant, causing abnormally low suction pressure while discharge remains normal.
CAR Troubleshooting & Diagnostics 3
A microwave oven turns on but does not heat food.
Which component is MOST likely faulty?