Signs of a Failing Water Heater Thermocouple > 자유게시판

If a hot water tap drips or the heater fails to start, the culprit is often a defective thermocouple. This small, metal device sits on the flame of the pilot of a gas water heater and keeps the gas valve open only when the pilot is lit. If it fails, your heater can lose heat or even pose a safety hazard. Being aware of the warning signs can help you catch problems before they turn into costly repairs.

1. Pilot Light Frequently Extinguishes
The most obvious sign is that the pilot flame repeatedly goes out. A healthy thermocouple creates a small electric current when exposed to heat. That current keeps the gas valve open. If the thermocouple is stuck in a "cold" state, the valve will close, and the pilot will extinguish. You may find yourself continuously relighting the flame.

2. Heater Turns Off While Still Hot
After the pilot is lit, the heater should stay on, heating water for the next 20‑30 minutes. A defective thermocouple will cause the gas valve to close early, despite the water remaining hot. You'll see the temperature fall suddenly, and the heater will need relighting every time.

3. Unusual Smells or Lack of Heat
A defective thermocouple can trigger the safety shut‑off, cutting off gas flow. This could cause a subtle chemical smell from the gas or, worse, a complete loss of heat. If you smell gas or find the water heater’s thermostat reading is far below the set temperature, check the thermocouple.

4. Pilot Light Flickers or Appears Dim
When a thermocouple is marginal, the pilot flame may look weak or flicker. This occurs as the gas valve cycles on and off intermittently. The pilot may look steady, but the underlying control is unstable.

5. Variable Water Temperature
If the water temperature swings erratically, from hot to lukewarm, the thermocouple could be miscalibrated. Even a small misalignment can result in the gas valve opening at wrong times.

6. Physical Wear and Corrosion
Check the thermocouple for visible wear signs. Corrosion, cracks, or a broken stem indicates it can’t produce sufficient voltage. Long-term, the metal may degrade, particularly in damp or humid environments.

7. Pilot Flame Lags Behind Thermocouple Response
Should you turn the pilot flame on manually and the thermocouple fails to respond quickly, it may be stuck. A lagging response often indicates the sensor is not properly detecting heat.

8. Alarm Codes or 名古屋市東区 給湯器 修理 LED Alerts
Modern gas water heaters often display error codes when the thermocouple fails. A flashing LED or panel code may indicate a "pilot light" or "sensor" problem.

9. Strange Sounds from the Heater
A rattling or clicking sound that occurs when the heater turns on can be a sign that the gas valve is flicking in and out—another symptom of a failing thermocouple.

10. Frequent Pilot Re‑lighting by a Professional
If a plumber has to relight the pilot repeatedly over a short period, it’s a clear indicator that the thermocouple isn’t functioning properly.

Fixing a Bad Thermocouple
Turn off the gas and let the heater cool down
Remove the old thermocouple using a wrench or pliers
Check for corrosion or damage; if found, replace it
Clean the connection spots and pilot flame region
Install the new thermocouple, aligning the stem with the pilot flame
Restore gas, relight the pilot, and check that the water heater stays on

If you’re uncomfortable working with gas appliances, call a licensed plumber
A timely replacement can prevent wasted gas, restore hot water, and keep your home safe