If gas logs won’t light, confirm gas is on, damper open, relight the pilot, and clean the thermocouple or thermopile; if you smell gas, call a pro.
Gas Logs Won’t Light: Quick Checks That Work
Start with safety. If you smell that rotten egg odor, step outside and call your gas company or emergency services from a safe spot. No switches, no phones, no flames near the appliance. If no odor is present, run the fast checks below before taking panels off.
- Is the main gas shutoff valve open? The handle should line up with the pipe.
- Is the fireplace damper open on vented sets? A closed damper blocks exhaust and many safety pilots will not allow ignition.
- Do you have gas to other appliances? A supply outage or empty propane tank will stop ignition.
- Power present? Intermittent pilot and IPI systems need house power or fresh batteries in the receiver and remote.
- Wall switch set to ON and not a timer or child lock? Try the manual rocker behind the lower trim if fitted.
- Glass front seated and latch engaged on sealed units? Many systems have interlocks that prevent firing if the glass is loose.
Fast Symptom Guide
| Symptom | Likely Cause | Try This |
|---|---|---|
| No pilot and no click | No gas, tripped breaker, dead batteries | Open valve, reset breaker, replace batteries in both handset and receiver |
| Pilot sparks but no flame | Air in line, clogged pilot orifice, gas off | Hold pilot knob longer, purge air per manual, clean pilot hood, verify gas on |
| Pilot lights then drops out | Weak flame not heating sensor, dirty or failed thermocouple or flame rod | Aim flame to touch sensor, clean with fine emery or Scotch-Brite, tighten probe nut |
| Pilot stays on, burner won’t light | Low thermopile output, bad switch, loose wiring | Measure millivolts, bypass wall switch, reseat spade connectors |
| Remote beeps, nothing lights | Receiver in learn mode, dead receiver batteries | Replace AA/AAA cells, re-sync remote and receiver, try wall switch |
| Intermittent boom on start | Delayed ignition from dirty burners | Vacuum burner ports, clean log ports, set logs per placement diagram |
Know Your Pilot System
Gas log sets use one of two common ignition schemes. Learning which one you have points you to the right fix.
Standing Pilot With Thermocouple
This style runs a small flame all season. The flame heats a thermocouple tip. That heat makes a tiny voltage which holds a safety magnet inside the gas valve. If the pilot goes out, the magnet drops and the gas shuts off. No house power needed for the pilot, though many sets still use a wall switch to open the main burner.
Intermittent Or Electronic Pilot
Intermittent pilot ignition, sometimes called IPI or electronic ignition, lights the pilot only when you call for heat. A flame sensor or thermopile proves flame and then the main burner opens. These systems need house power or batteries for the spark module and control board.
Pilot Is On But The Burner Won’t Light
If the pilot holds but the main flame never starts, check the control loop. The wall switch or remote simply carries a small millivolt signal from the thermopile back to the gas valve. Any weak link drops voltage and the valve never opens.
- Measure thermopile output across TP and TH/TP with the switch closed. Many valves need around 300–500 mV under load.
- Bypass the wall switch by joining the two control wires at the valve. If the burner lights, replace the switch or clean its contacts.
- Inspect spade terminals and wire nuts. Oxidation or a loose push-on connector will waste precious millivolts.
- Look for soot on burner ports or logs sitting out of position. Misplaced logs can deflect the pilot flame away from the sensor and starve the main burner of crossover flame.
Pilot Won’t Stay Lit: Causes And Fixes
Weak Flame Not Heating The Sensor
The pilot flame should be sharp and blue with a small yellow tip. It must wrap the thermocouple or flame rod by at least half the tip. If the flame barely touches, bend the pilot hood or nudge the bracket so the flame kisses the sensor. Do not crush the tubing.
Dirty Thermocouple Or Flame Rod
Oxide on the probe acts like insulation. With the gas off and the assembly cool, polish the probe lightly with fine abrasive pad until clean metal shows. Wipe dust away. Re-light and confirm the pilot now holds.
Failed Thermocouple Or Thermopile
Thermocouples can wear out. If cleaning and flame adjustment still fail, replace the probe. On units with a thermopile, check open-circuit voltage. Fresh thermopiles often read 600–800 mV open and drop under load. A sagging reading points to replacement.
Drafts And Air In The Line
Strong downdrafts or a long unused gas run can snuff a small flame. Shield the pilot from direct air, then hold the pilot knob long enough to purge air per the manual. If wind enters the chimney, crack a nearby window during lighting to balance room pressure.
Gas Log Won’t Ignite: Safe Fixes And When To Stop
Work only when there is no gas odor and the set is cool. Keep a spray bottle with mild soap and water nearby for leak checks on threaded joints you touched. Bubbles mean a leak and the work stops until a licensed tech repairs it.
Cleaning The Bits That Do The Work
Dirt is the top spark thief. A yearly clean keeps ignition crisp, quiet, and safe.
Thermocouple, Thermopile, And Flame Sensor
- Shut off the gas. Let everything cool.
- Remove the pilot assembly shroud. Photograph the layout so re-assembly is easy.
- Lightly polish the probe with a fine pad. Do not sand grooves into it.
- Reseat the compression nut on a thermocouple snugly. Do not over-tighten.
- Re-route any wires away from sharp edges and hot plates.
Pilot Orifice And Burner Ports
Use compressed air or a soft brush on the pilot hood and orifice. Vacuum burner ports and the firebox floor. Reposition the logs per the placement diagram; ports blocked by sand or shards will cause delayed ignition and small explosions at start.
Airflow, Venting, And Damper Settings
Vented sets need an open damper and a sound chimney path. Vent-free sets use room air and require the room size and fresh air openings listed on the rating plate. If a carbon monoxide alarm sounds or you see sooting on doors or walls, shut the set off and call a licensed tech.
For annual service and safe setup tips from an industry trade group, see the HPBA gas-burning maintenance page. For leak response guidance, review the NFPA fuel gas leak steps.
Power, Controls, And Remotes
Many “no light” calls trace back to tiny details in the control chain.
- Replace receiver batteries and remote batteries together. Weak cells pass pairing but fail under spark load.
- Slide the receiver switch to ON to bypass the handset during tests. If the unit lights, the remote or receiver needs pairing or replacement.
- Check wall switch continuity. A soot-dusted switch can drop millivolts. A simple jumper at the valve will tell you fast.
- Look for overheated receivers tucked in the firebox cavity. Move the box to a cooler pocket per the manual.
Common Safety Devices And Locations
| Device | What It Senses | Typical Location |
|---|---|---|
| Thermocouple | Pilot flame heat to hold the safety magnet | Next to pilot flame, copper tube to valve |
| Thermopile | Pilot flame heat to power valve and switch loop | Beside pilot, two thicker leads to valve |
| Flame sensor rod | Flame rectification on IPI systems | At pilot, wire to control board |
| Spill switch | Vent spill or draft reversal | On draft hood or near flue outlet |
| Low O2 sensor (Oxygen Depletion) | Room oxygen level on vent-free sets | Integrated into pilot assembly |
| Glass latch/door switch | Closed viewing glass on sealed units | At the frame or hinge |
When To Call A Pro
Stop DIY work and pick up the phone if any of these show up:
- Any gas odor, hissing, or blowing from the firebox, valve area, or meter.
- Soot on logs, doors, or walls, or a lazy orange main flame.
- Cracked log media or broken burner parts.
- Repeated pilot drop-out after cleaning and flame aiming.
- Control board faults, melted wires, or tripped spill switches.
Out of the box steps to light and restart also live in manufacturer guides. Your owner’s manual shows the typical sequence and pilot positions used by many brands.
Quick Re-Light Sequence For Most Sets
- Turn the gas control to OFF and wait five minutes for any gas to clear.
- Set the control to PILOT. Hold the knob in and click the igniter until the pilot lights.
- Keep holding the knob in for 30–60 seconds so the probe heats fully, then let go. The pilot should stay on.
- Turn the control to ON. Return the wall switch or remote to ON and watch for smooth burner crossover.
- If the flame lifts or pops, kill the gas, let cool, and clean burner ports before the next try.
Practical Upkeep Tips
- Schedule yearly service before heating season. A tech will test millivolts, clean burners, verify venting, and check gaskets.
- Vacuum dust from the firebox base once a month during heavy use.
- Keep spare AA/AAA cells for receivers and remotes near the fireplace.
- Label the shutoff valve location clearly and the breaker that feeds the outlet or blower.
- Store the log placement diagram with the manual to prevent misplacement after cleanings.
Keep vents clear and gaskets intact for steady starts.