How much does it cost to fix a furnace pilot that won't stay lit?

The short answer

A pilot that won't stay lit is one of the cheapest furnace problems to fix, and one of the most common. in most cases it's a thermocouple that's worn out or a pilot orifice that's clogged.

That's a universal thermocouple, some cleaning supplies, and maybe a small wrench you didn't already own.

Hire it out and expect $150–$700. The part is dirt cheap; you're paying for the trip, the labor, and a tech who'll confirm the gas valve and flue are safe before leaving.

The good news: catching this in summer is the ideal time. No heat emergency, no rush pricing, and you've got weeks to sort it out before you need heat.

Where the money goes

The DIY math is simple. A universal thermocouple is $10 to $18.

If you already own basic tools, your real out-of-pocket is closer to $15 for just the part.

The pro range of $150–$700 breaks down mostly as labor and the service call. Most companies have a minimum trip charge of $90 to $150 before they touch anything.

Labor for a thermocouple swap is usually 30 to 60 minutes, but you're often paying a flat diagnostic-plus-repair rate. The part markup is small because the part itself is cheap.

The higher end of the pro range shows up when there's corrosion to fight, a valve to inspect closely, or the tech recommends a fuller tune-up while they're in there.

If it turns out to be the gas valve, that's a separate job entirely: figure $350 to $700 installed depending on your furnace model and how buried the valve is.

How we built these numbers

The cost ranges come from typical 2026 US pricing for thermocouple parts, common service-call minimums, and standard labor times for gas furnace pilot repairs.

DIY figures assume a universal thermocouple plus basic supplies and a couple of tools a homeowner might need to buy. If you already have tools, expect to spend far less.

Pro figures reflect a licensed HVAC tech's trip charge, diagnostic, labor, and part, at national average rates. Dense metro areas run higher; rural areas can run lower.

Gas valve replacement is priced separately because it's a different job with its own part and it's the main thing that pushes a simple visit into a bigger bill.

Your actual quote depends on local labor rates, how accessible the valve is, and whether the tech finds anything else worth addressing while the panel is off.

Why the pilot keeps going out

Standing-pilot furnaces have a built-in safety trick. The pilot flame heats a probe called a thermocouple, which generates a tiny voltage (roughly 25 to 30 millivolts).

That voltage energizes an electromagnet inside the gas valve. As long as the magnet is powered, the valve stays open and the pilot keeps burning.

The second the thermocouple stops making enough voltage, the magnet drops, the valve snaps shut, and the pilot dies. That's exactly what you're seeing when you release the knob and the flame goes out.

So the flame going out isn't the furnace being broken. It's the safety system doing its job because the signal that says 'flame is present' isn't strong enough anymore.

What's actually causing it

Start with the thermocouple. It's the most common failure by a wide margin, and it's a wear part that just gives out after a decade or so of heat cycling.

Next, look at the flame itself. A weak, yellow, or dancing pilot flame usually means a clogged orifice. Dust and spider webs love that little tube during the off-season.

Then check the connection. A loose or corroded nut where the thermocouple threads into the valve will fake a dead thermocouple perfectly. It's a two-minute check that saves a part swap.

Drafts are the sneaky one in summer. Open windows and running fans can literally blow the flame sideways off the probe. Close things up and retry before you buy any parts.

If a fresh thermocouple and a clean flame still won't hold, you're into gas valve territory. That's the expensive, pro-only end of the range.

Work through it in order

Don't jump straight to buying parts. Half the time the fix is free.

First, the 60-second test. Light the pilot and hold the knob down for a full minute so the thermocouple gets fully hot before you let go. A lot of people release too early and misread a good thermocouple as bad.

If it dies after a proper 60-second hold, rule out drafts. Close basement windows, kill any fans, retry.

Still dying? Shut the gas off, let it cool, and look at the flame next time you light it. Weak and yellow means clean the orifice. Strong and blue but still won't hold means the thermocouple or its connection.

Snug the connection nut before you replace anything. If that doesn't do it, swap the thermocouple. Match the length exactly so the tip sits in the hottest part of the flame.

• 60-second knob hold test
• Rule out drafts (windows, fans)
• Inspect flame color and strength
• Tighten the thermocouple connection nut
• Clean the pilot orifice if flame is weak
• Replace the thermocouple if all else fails

Should you DIY this one?

This is genuinely DIY-friendly if you respect the gas side of it. A thermocouple swap is one nut at the valve, one bracket clip at the pilot, and matching the length.

The line I draw: if you can confidently shut off the gas, wait five minutes, and check your work with soapy water afterward, you can do this. If any of that makes you nervous, don't.

Call a pro if the connection nut is corroded solid, if you smell gas at any point, or if a new thermocouple doesn't fix it. That last one means the valve is suspect, and valves are not a DIY part.

Also call a pro if you're not sure whether you even have a standing pilot. Newer furnaces (roughly post-2010) mostly use electronic ignition, which has no thermocouple and no pilot to relight.

How long can you put it off?

In summer, honestly, you've got room. A dead furnace pilot isn't an emergency when it's 90 degrees out.

But don't let it slide until October. The moment cold weather hits, every HVAC company in town is slammed, and a simple thermocouple job turns into a week-long wait plus premium pricing.

The real risk of waiting is timing, not damage. Diagnose it now, fix it now, and you'll flip the furnace on in fall without a second thought.

One caveat: if you suspect a draft or flue issue is behind the outages, don't just relight and forget it. A backdrafting flue is a carbon monoxide risk once the furnace actually and that needs a pro before winter.

Gas safety, plainly

You're working near a live gas line, so a few rules aren't optional.

Set the gas control to OFF and wait at least five minutes before touching the pilot assembly. This lets any lingering gas clear.

If you ever smell rotten eggs, stop. Don't flip switches, don't light anything. Get outside and call your gas utility or 911.

After any reassembly, spray soapy water on the connections and watch for bubbles with the gas back on. Bubbles mean a leak, and that means shut it down and call a pro.

Keep a working carbon monoxide detector near your sleeping areas. CO is odorless, and a furnace with combustion problems is exactly the kind of thing it catches.

Does your furnace age change the call?

A furnace under 15 years old with a dead thermocouple? Easy fix, worth every dollar. This is routine wear.

A furnace 20-plus years old that's now stacking up repairs is a different conversation. The thermocouple fix is still cheap, but it might be the first of several.

If you're at that age and the pilot problem shows up alongside a rusty heat exchanger, a noisy blower, or rising gas bills, get a replacement quote before you keep patching.

Most gas furnaces run 15 to 20 years. Fixing a $15 part on a 22-year-old unit is fine, but don't talk yourself into a $600 valve on one that's near the end anyway.