An Intertherm furnace pilot light is a small flame that ignites the burner when heat is requested. While many modern furnaces use electronic ignition, some Intertherm models still rely on a standing pilot light. Understanding how it works, common failure signs, and safe relighting steps helps homeowners stay warm and avoid unnecessary service calls. This guide covers how the pilot light functions, typical issues, safety precautions, relighting steps, maintenance tips, and when to call a professional. The information is written for a general U.S. audience and emphasizes practical, actionable guidance.
What Is The Intertherm Furnace Pilot Light
The pilot light is a small, continuously burning flame that provides a flame source for the main burner. In Intertherm gas furnaces, the pilot is controlled by a gas valve and a safety device, commonly a thermocouple or thermopile, which detects the flame and signals the gas valve to stay open. A steady blue flame indicates proper combustion; a yellow or flickering flame can indicate incomplete combustion or a dirty pilot assembly. If the pilot flame goes out, the gas valve will shut off to prevent gas buildup.
How The Pilot Light Works In A Gas Furnace
When the thermostat calls for heat, the gas valve opens to the pilot line and main burner. The standing pilot flame heats the thermocouple, producing a millivolt signal that keeps the gas valve open. If the pilot goes out, the thermocouple cools, the signal drops, and the valve closes to stop gas flow. Some Intertherm models use an intermittent ignition system instead of a standing pilot; these rely on an electronic spark or hot surface ignitor to light the burner. Regardless, a reliable flame sensor and clean components are essential for safe operation.
Common Reasons The Pilot Light Goes Out
- Drafts or direct airflow near the furnace can blow out the flame.
- Dirty or misaligned thermocouple or thermopile.
- Dirty or clogged pilot orifice restricting gas flow.
- Weak gas supply due to low pressure or closed valve.
- Worn gas control valve or faulty safety switch.
- Thermal switch or limit switch tripping due to overheating.
Safety Considerations When Handling Or Relighting A Pilot
Gas furnaces emit natural gas that is odorized with mercaptan to aid detection. If a gas smell is detected, evacuate and call the gas company or emergency services. Never relight a pilot with a strong gas odor. Work in a well-ventilated area and keep flammable materials away from the furnace. If you are unsure about gas lines, components, or safety, contact a licensed HVAC technician. Regular CO detectors and furnace venting inspections improve safety.
Step-By-Step: Relighting The Pilot Light
The exact procedure can vary by model. Always consult the owner’s manual for model-specific instructions. A typical standing-pilot relight process is:
- Turn the thermostat off and set the gas control to OFF for five minutes to vent accumulated gas.
- Locate the access panel and open the furnace cabinet to access the gas valve and pilot assembly.
- Turn the control knob to PILOT or ON, depending on the model. Press and hold the reset/light button if equipped.
- While holding, light the pilot flame with a long match or a long-reach lighter. Keep the flame near the pilot until lit.
- Hold the knob in the PILOT position for 30-60 seconds to heat the thermocouple, then release and return the knob to ON or HEAT.
- Close the cabinet, restore power to the furnace, and set the thermostat to desired heat.
When To Call A Professional
Call a technician if the pilot will not light after repeated attempts, if the flame goes out immediately after relighting, if you smell gas or CO alarms indicate danger, if you notice damaged wiring, corrosion, or soot on the furnace, or if the furnace is not producing heat efficiently after relight. A professional can test gas pressure, replace thermocouple, clean pilot and valves, and verify proper venting and CO safety.
Maintenance Tips To Prevent Pilot Light Problems
Regular maintenance helps prevent lighting problems. Suggestions:
- Schedule annual professional inspections for gas furnaces.
- Keep the furnace area clean and unobstructed to maintain proper airflow.
- Inspect the thermocouple or flame sensor and replace if bent or worn.
- Clean the pilot orifice and ensure a clean flame with a blue color.
- Test safety controls and CO detectors regularly.
Common Problems, Quick Fixes, And Preventive Measures
Below is a quick reference to common symptoms, causes, and actions. This section supplements the step-by-step relighting guidance and emphasizes preventive care.
| Symptom | Possible Cause | Action |
|---|---|---|
| Pilot won’t light | No gas supply, faulty thermocouple, dirty pilot | Check gas valve, inspect pilot tube, clean or replace thermocouple |
| Flame is yellow or flickering | Dirty burner, insufficient air, gas pressure issue | Clean burner, check vents, have gas pressure tested |
| Pilot goes out after lighting | Thermocouple misalignment or dirty | Reposition or clean thermocouple; inspect flame |
| Frequent outages after short run | Overheating or safety switch trips | Check for proper venting; ensure return air and registers are clear |