How To Fix A Pilot Light On A Furnace

Troubleshooting Your Furnace Pilot Light: A Homeowner's Guide

A furnace pilot light that won't stay lit can be a frustrating problem, especially during the colder months. Before you call a professional, you can try a few simple troubleshooting steps yourself. This guide will walk you through the process, from initial checks to potential solutions. Remember, if you're uncomfortable with any of these steps, or if the problem persists, contacting a qualified HVAC technician is always the safest option.

Safety First!

Before you begin, always turn off the gas supply to your furnace. Locate the gas shut-off valve, usually a yellow handle on the gas pipe leading to the furnace, and turn it perpendicular to the pipe. This cuts off the gas supply and prevents any potential gas leaks. Also, make sure you have adequate ventilation in the area.

Here's a list of tools you might need:

Screwdrivers (Phillips head and flathead)
Wrench (for gas line connections, if necessary)
Small brush or compressed air
Multimeter (optional, for testing thermocouple)
New thermocouple (if necessary)
Matches or a long lighter

Step 1: Initial Inspection

Begin by visually inspecting the pilot light assembly. Look for any obvious signs of damage, such as:

Cracked or broken parts
Loose connections
Excessive rust or corrosion
Debris blocking the pilot light opening

If you find any of these issues, address them before proceeding. Clean any debris with a small brush or compressed air. Tighten any loose connections. If parts are broken or severely corroded, they may need to be replaced.

Step 2: Checking the Gas Supply

Even if you think you have gas, it's worth double-checking. Make sure your gas appliances (like your stove) are working. If not, the problem might be with your main gas supply, and you should contact your gas company.

Step 3: Lighting the Pilot Light

Most modern furnaces have instructions printed directly on the unit for relighting the pilot. However, here are the general steps:

Turn the gas valve knob on the furnace to the "Pilot" setting.
Press and hold the reset button (usually red or black) while simultaneously using a long lighter or match to ignite the pilot light.
Continue holding the reset button for 20-30 seconds. This allows the thermocouple to heat up.
Release the reset button. If the pilot light stays lit, turn the gas valve knob to the "On" position. If the pilot light goes out, proceed to the next step.

Step 4: The Thermocouple: The Prime Suspect

The thermocouple is a small, copper rod that sits in the pilot flame. It generates a small electrical current when heated, which keeps the gas valve open. If the thermocouple is faulty, it won't generate enough current, and the gas valve will close, extinguishing the pilot light.

Here's how to troubleshoot the thermocouple:

Clean the Thermocouple: Use a fine-grit sandpaper or steel wool to gently clean the tip of the thermocouple. Sometimes, a layer of soot or corrosion can prevent it from working properly.
Check the Thermocouple Connection: Ensure the thermocouple is securely connected to the gas valve. A loose connection can disrupt the electrical current.
Test the Thermocouple (Optional): Using a multimeter set to millivolts (mV), you can test the thermocouple's output. While holding the thermocouple in a flame, it should generate a reading of at least 20-30 mV. If the reading is significantly lower, the thermocouple is likely faulty and needs to be replaced.

Replacing a Thermocouple: Replacing a thermocouple is a relatively simple task. First, turn off the gas supply to the furnace. Disconnect the old thermocouple from the gas valve and the pilot light assembly. Install the new thermocouple, ensuring it's properly positioned in the pilot flame. Tighten the connections securely, but don't overtighten. Turn the gas supply back on and relight the pilot light, following the steps outlined earlier.

Step 5: The Pilot Orifice: Clearing Obstructions

The pilot orifice is a tiny hole that allows gas to flow to the pilot light. Over time, this orifice can become clogged with dust, debris, or spider webs, restricting gas flow and causing the pilot light to go out. You can clean the pilot orifice using a small wire or needle.

Caution: Be extremely careful when cleaning the pilot orifice. Do not enlarge the hole, as this can affect the pilot flame and the furnace's efficiency.

Step 6: The Gas Valve: Proceed with Caution

The gas valve controls the flow of gas to the furnace. If the gas valve is faulty, it may not be supplying enough gas to the pilot light, causing it to go out. Troubleshooting the gas valve is more complex and potentially dangerous. If you suspect a problem with the gas valve, it's best to call a qualified HVAC technician.

Potential signs of a gas valve issue:

A weak or flickering pilot flame, even after cleaning the thermocouple and pilot orifice.
A hissing sound coming from the gas valve.
Difficulty lighting the pilot light, even after multiple attempts.

Step 7: The Flame Sensor (For Furnaces with Electronic Ignition)

Some newer furnaces use an electronic ignition system instead of a traditional pilot light. These systems typically have a flame sensor, which detects the presence of a flame and allows the furnace to continue operating. If the flame sensor is dirty or faulty, it can shut down the furnace. Clean the flame sensor with fine steel wool or sandpaper. The flame sensor is usually a ceramic rod near the main burner.

When to Call a Professional

While many pilot light problems can be resolved with simple troubleshooting, there are times when it's best to call a professional HVAC technician. Here are some situations where professional help is recommended:

You're uncomfortable working with gas appliances.
You've tried all the troubleshooting steps and the pilot light still won't stay lit.
You suspect a problem with the gas valve or other major furnace components.
You smell gas, even after shutting off the gas supply.
Your furnace is old or has a history of problems.

Estimated Repair Costs

The cost of repairing a furnace pilot light can vary depending on the problem and the technician's rates. Here are some general estimates:

Thermocouple Replacement: $75 - $200
Pilot Orifice Cleaning: $75 - $150 (often included in a service call)
Gas Valve Replacement: $200 - $600+ (this is a complex repair)
Service Call Fee: $75 - $150 (this is a base fee for a technician to come to your home)

Note: These are just estimates. It's always best to get a quote from a qualified HVAC technician before proceeding with any repairs.

Preventative Maintenance

Regular furnace maintenance can help prevent pilot light problems and extend the life of your furnace. Here are some tips:

Schedule an annual furnace inspection and tune-up with a qualified HVAC technician.
Replace your furnace filter regularly (every 1-3 months).
Keep the area around your furnace clean and free of debris.

Common Reasons for a Pilot Light to Go Out:

Dirty or faulty thermocouple
Clogged pilot orifice
Drafts blowing out the flame
Low gas pressure
Faulty gas valve
Dirty flame sensor (for electronic ignition systems)

By following these steps, you can troubleshoot your furnace pilot light and potentially save yourself a service call. However, remember to prioritize safety and call a professional when needed. A properly functioning furnace is essential for a comfortable and safe home.