Why Won’t My Gas Fireplace Pilot Light Stay Lit? | Space Fireplace Ser
Space Fireplace Services — DFW chimney & fireplace specialists. Free inspection, written quote, no surprise fees.
Your fireplace should feel like the warmest room in the house — not a problem to manage: why won’t my gas fireplace pilot light stay lit is one of the most common questions we get from Plano, Frisco, McKinney, Allen and the north DFW corridor 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 — Quick read
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
Before you do anything, please read this: 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.)
When to call a pro
If the home-side checks don’t get your fireplace back to the experience you want. Space Fireplace Services covers Plano, Frisco, McKinney, Allen, and the north DFW corridor — we treat your fireplace like the design centerpiece it is, and the technician who diagnoses it is the same one who follows up.
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.
Related guides & services
Ready when you are
Schedule a visit so you can get back to enjoying the space — fall and winter slots fill fast. Call (469) 992-4912 or use the contact form.
Our Sister Companies — Specialists in Related Services
Texas Service Experts is part of a network of CSIA-certified chimney specialists. Depending on your specific need:
- Texas Service Experts — general chimney sweep/inspection
- Texas Chimney Experts — chimney repair/masonry