No-heat and weak-heat faults have different causes.
Start Here
Confirm the appliance is receiving the correct supply.
Check airflow or water flow requirements.
Inspect settings and sensors.
Test heaters unplugged when access is safe and specified.
A useful diagnosis turns a vague complaint into a smaller technical question. No-heat and weak-heat faults have different causes. For poor heating, concentrate on power, heat, airflow, water and mechanical loads. Use every working function as evidence: if one stage still behaves normally, that fact eliminates causes that would have stopped the appliance earlier in the sequence.
Observe the timing before touching anything. Note what happens immediately after Start, what changes just before the fault, and what remains normal afterward. Lights, relay clicks, water movement, motor or fan sounds, heat, vibration and error codes are useful only when tied to a point in the cycle. A fault that appears instantly is a different problem from one that appears only after the machine warms up or reaches a later stage.
Begin with the cheapest conditions to verify: confirm the appliance is receiving the correct supply, then check airflow or water flow requirements. Do not merely glance at them. Compare the actual condition with the manual, correct anything obviously wrong, and retest before moving deeper. Simple installation, maintenance and user-setting problems regularly imitate failed electrical parts.
If those checks pass, move to inspect settings and sensors. Then decide whether test heaters unplugged when access is safe and specified can be evaluated safely with power isolated. Choose one test that answers one question: blocked or clear, open or closed, free or jammed, intact or electrically open. If a test result would not change your next decision, the test is probably not worth doing.
Avoid assuming the heater is always bad, ignoring low airflow, and performing live heater tests without training. All three skip evidence and can turn a minor fault into an expensive one. After a correction, reassemble guards and connectors, restore normal settings, and reproduce the original operating conditions. A single successful start is not proof; the original symptom must stay gone through the stage that used to fail.
A Safe Step-by-Step Check
Document the exact symptom and pay special attention to confirm the appliance is receiving the correct supply.
Remove external causes first; specifically verify check airflow or water flow requirements.
With power isolated where required, inspect inspect settings and sensors and then evaluate test heaters unplugged when access is safe and specified only if it can be done safely.
Reassemble fully and run a controlled test under the conditions that previously caused the fault.
Common Beginner Mistakes
Assuming the heater is always bad.
Ignoring low airflow.
Performing live heater tests without training.
STOP AND GET HELP: If the next useful test requires exposed live mains, defeating a safety interlock, opening a sealed refrigeration circuit, disturbing gas controls, or entering a microwave high-voltage section, the diagnosis has reached the professional-service boundary.