Why Does My Furnace Pilot Light Keep Going Out?

Is your furnace pilot light repeatedly shutting off and leaving you out in the cold? A temperamental furnace pilot that won't stay lit can quickly become the bane of any homeowner's existence during the chilly winter months. But don't despair - most causes of a faulty furnace pilot are easily diagnosed and repaired if you know where to start.

We'll also share pro tips to help prevent future furnace pilot problems through improved maintenance and safety.

What Causes My Furnace Pilot to Repeatedly Go Out?

Before attempting to relight a furnace pilot or calling an HVAC technician, it helps to understand what's causing the issue in the first place. Here are the most common culprits behind a furnace pilot that won't stay lit:

Dirty Thermocouple Connection

The thermocouple generates a small voltage to signal the gas valve to stay open and allow gas flow to the pilot light. But over months of use, grime and corrosion can build up on the thermocouple connection point and compromise the circuit.

Carefully scrubbing the thermocouple tip and interior hole on the gas valve can often restore a solid connection. If cleaning doesn't work, a faulty thermocouple that isn't generating the proper voltage will need replacing.

Thermopile Voltage Too Low

A dirty or failing thermopile is another common source of continuous furnace pilot shut-offs. The thermopile works similarly to the thermocouple, but on a larger scale to power the main gas valve circuit for heating home rooms.

Use a multimeter to check your thermopile is producing at least 500-600 mV when the pilot is lit. If the voltage measures low, try cleaning the thermopile probe with a soft brush before replacing the part.

Weak Pilot Flame

Sometimes the pilot light flame is simply too small or weak to properly preheat the thermocouple or thermopile sensors. This can happen when debris clogs the pilot orifice opening or if gas pressure in the line drops.

Carefully increasing gas flow to the pilot assembly with an adjustment screw on the gas valve will often strengthen the flame. Be sure to set screw flush after adjusting and check your pilot bracket is aligned correctly.

Combustion Air Supply Issues

For the pilot flame to stay stable and lit, your furnace needs adequate airflow for combustion and ventilation. A restricted air filter, blocked flue opening, or negative pressure from bathroom fans can starve the pilot light.

Inspect your furnace blower compartment and flue connections for any noticeable airflow restrictions. Opening a window briefly can also offset negative pressure concerns pulling combustion gases back down the flue.

Step-By-Step Guide to Relighting Furnace Pilot

Armed with a better understanding of what causes a faulty pilot light, you're ready to tackle the repair. Follow this simple procedure to safely relight your furnace pilot when it goes out:

Turn Off Gas Valve & Allow Ventilation

Before re-lighting, shut off the manual gas valve leading to your furnace and wait at least 5 minutes for any residual gas in the chamber to dissipate.

Set Gas Valve to Pilot Position

Turn the gas control switch to the 'pilot' setting instead of 'on/off. This redirects gas flow to just the pilot assembly instead of the main furnace burner.

Push Valve Reset Button & Light Pilot

Press and hold the reset button down while immediately lighting the pilot tube opening with a long fireplace lighter. Hold button down for 60 seconds after lighting.

Watch Pilot Flame Closely

Keep an eye on the pilot flame to ensure it stays lit and engages the safety thermocouples. If it goes back out, repeat re-lighting steps until the flame remains stable.

Set Gas Valve Back to "On"

Finally, turn the gas control valve to the full 'on' position again. Verify the blower turns on and that heat starts flowing from registers as normal.

Preventative Furnace Pilot Maintenance

Beyond addressing immediate furnace pilot issues, completing routine maintenance helps avoid many pilot problems in the first place. Here are some handy tips:

Schedule Annual Furnace Inspections

Technicians can spot early signs of wear on ignition components to replace during off-season. Annual inspections also catch bigger issues before they become pilot failure emergencies mid-winter.

Change Air Filter Every 2-3 Months

Clogged furnace filters reduce system airflow needed to keep the pilot flame stable. Mark your calendar to replace filters to prevent debris build-up near the burner.

Install CO Monitors Near Bedrooms

Carbon monoxide sensors provide an extra alert system if the pilot light happens to blow out while everyone is asleep or away from home for extended periods.

FAQs: Furnace Pilot Troubleshooting

Having trouble getting your faulty furnace pilot light to cooperate? Here are answers to some of the most common questions homeowners have about pilot issues:

Why Does My Pilot Light Keep Going Out Overnight?

Furnace pilots often blow out overnight as temperatures drop and combustion airflow decreases. Poorly insulated attics and basements also contribute to greater temperature swings that destabilize pilot flames at night.

How Often Should I Get My Furnace Serviced?

Most HVAC companies recommend annual furnace tune-ups to inspect all systems ahead of winter. At minimum, have your pilot assembly checked every 2-3 years or if you notice any recurring issues igniting.

Is My Pilot Light Hard to Light Because It's Dirty?

Yes, dirt, corrosion, and debris can certainly make an older pilot light more difficult to ignite. Carefully cleaning the thermocouple, thermopile, and orifice holes can help ease lighting issues.

Scheduling professional pilot cleaning during routine furnace maintenance can also offset any debris concerns before it becomes a problem.

Should I Relight My Furnace Pilot Light?

In most cases, relighting your furnace pilot is perfectly safe as long as gas valves are turned fully off prior to any repair attempts.

However, if the pilot won't stay lit no matter troubleshooting done or you smell leaking gas, call your HVAC technician for emergency furnace repairs.

Why Is My Furnace Taking Long to Ignite?

Slow or delayed furnace ignition often comes down to a weak pilot flame struggling to activate the thermocouple safety switch and engage the main gas valve.

Adjusting gas flow at the regulator or cleaning dirty flame sensor tips can typically resolve slow ignition furnaces in older units.

Furnace pilot lights may seem mysterious initially, but fundamental issues usually prove repairable with some handy troubleshooting. However, for complex electrical, gas, or airflow-related repairs, rely on a professional for assistance.

Also contact emergency HVAC services immediately if:

• You smell gas anywhere in the home
• The pilot light won't stay lit after repeated attempts
• Burners backfire, produce thick black smoke or make loud noises
• The main blower isn't powering on to push warmed air