Why Won’t My Gas Fireplace Pilot Light Stay Lit? | Texas Service Exper
Texas Service Experts — DFW chimney & fireplace specialists. Free inspection, written quote, no surprise fees.
Quick honest answer first, then the diagnostic flow: why won’t my gas fireplace pilot light stay lit is one of the most common questions we get from Dallas-Fort Worth Metroplex homeowners. Below is the diagnostic flow we use on-site, written so you can run it yourself before you spend money on a service call.
TL;DR — Here’s the short version
If the pilot lights but goes out within seconds of releasing the control knob, the cause is almost always a failing thermocouple (single-pilot system) or thermopile (millivolt system). Less commonly: a dirty pilot orifice, a draft blowing the flame off the sensor, or a failing gas valve. The thermocouple/thermopile is a 30-minute fix; gas valve replacement is a bigger job.
Why we see this in DFW
DFW homes with gas fireplaces installed 10+ years ago — common in early-2000s Plano, Frisco, McKinney builds — are right in the thermocouple-failure window now. We also see pilot issues spike in winter when our cold fronts drop attic temps and old gas lines develop minor moisture issues.
⚠ Safety first
Important safety note before you start: Gas fireplaces involve a fuel-burning appliance and require correct combustion-air supply, gas-pressure, and venting. If you smell gas at any point — even faintly — leave the area, do not operate any electrical switches, and call your gas utility’s emergency line. Do not attempt repairs you’re not confident in.
Diagnostic flow — work through in order
Run these steps one at a time. Each step ends with a stop-check so you know whether to keep going or call us.
- 1. Confirm the problem first — light it and time it — Light the pilot per the fireplace manual. Hold the control knob in for the full 30-60 seconds the manual specifies, then release. Time how long until it goes out. (Out within seconds = sensor problem (thermocouple/thermopile). Stays lit a while then dies = different issue (dirt, draft). If this fixes it: STOP. If not: continue.)
- 2. Check the pilot flame visually — A healthy pilot flame is steady, blue, and wraps around the thermocouple/thermopile sensor tip. Yellow, weak, or flame that doesn’t touch the sensor = your problem is here. (Weak/yellow/misaligned flame = sensor isn’t getting heated properly, so it doesn’t signal the gas valve to stay open. If this fixes it: STOP. If not: continue.)
- 3. Clean the pilot orifice — Turn off the gas at the shut-off valve. Wait 5 minutes. With a soft brush or compressed air, clean any visible dust or spider-web debris from the pilot assembly. Spider webs in the orifice are surprisingly common (pest called gas-line spiders specifically nests in them). (Dirty orifice cleaned = sometimes that’s the whole fix. If this fixes it: STOP. If not: continue.)
- 4. Check for drafts on the pilot — Open the fireplace front. Light a match near the pilot area. If the match flame is constantly disturbed, you have a draft pulling the pilot off the sensor. Common cause: a missing or cracked glass front on a direct-vent unit. (Visible draft = fix the draft (replace gasket, reseat glass) before replacing parts. If this fixes it: STOP. If not: continue.)
- 5. Test the thermocouple/thermopile (if you have a multimeter) — With pilot lit and held, a healthy thermocouple reads 25-35 mV across the connection. A thermopile reads 300-750 mV. Below those ranges = part is failing. (Out-of-range reading confirms the part needs replacement. If this fixes it: STOP. If not: continue.)
- 6. Replace the thermocouple or thermopile — This is a $30-$-+ part and a 30-minute job for someone comfortable with gas appliances. If you’re not, this is exactly when to call a pro — gas-related work where one missed step matters. (Part replaced + secured = pilot should stay lit. If not, the gas valve itself may be failing. If this fixes it: STOP. If not: continue.)
- 7. If it still won’t stay lit, the gas valve is suspect — A failing gas valve (the brass body the thermocouple feeds into) means the sensor is working but the valve no longer holds open. This is a $250-$-+ part plus labor and is firmly pro-only territory. (Failed gas valve = scheduled gas-fireplace repair, not DIY. If this fixes it: STOP. If not: continue.)
What it costs to diagnose & fix (DFW, 2026)
Real DFW market ranges. Inspection always comes with a written quote before any repair work begins — no hidden fees.
| Service | Typical range |
|---|---|
| Level 1 inspection (gas fireplace diagnostic) | $89 |
| Pilot orifice cleaning + adjustment | $100-$-+ |
| Thermocouple replacement | $150-$-+ |
| Thermopile replacement | $200-$-+ |
| Gas valve replacement | $400-$-+ |
| Full gas system inspection (any leak signs) | $199-$-+ |
Frequently asked questions
How long should a thermocouple last?
Typically 8-12 years. They’re a wear part — the sensor metal degrades with each heat cycle. If yours is original and 10+ years old, replacing it preventively is reasonable.
Why does the pilot work in winter but not summer (or vice versa)?
Temperature affects gas pressure and combustion-air density. Marginal systems work in one season and fail in the other. This usually means a part is borderline and worth replacing rather than waiting for a full failure.
Is a yellow pilot flame dangerous?
Yellow pilot indicates incomplete combustion, which means more carbon monoxide and soot. It’s also a sign your sensor isn’t getting properly heated. Address it — don’t run the fireplace with a yellow pilot.
Can I replace the thermocouple myself?
If you’re comfortable with gas appliances, can shut off gas at the valve, and follow the manufacturer manual exactly — yes. If any of that gives you pause, this is a $150-$-+ service call worth paying.
Why does my pilot light only go out at night?
Likely a draft. Cooler nighttime temps + tighter house + wind direction create downdraft that the daytime conditions don’t. Look for envelope sealing issues around the fireplace chase.
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Our Sister Companies — Specialists in Related Services
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