HVACopediaNapoleon · Gas fireplace troubleshooting
Main burner goes out; pilot stays on
What is going on
Pilot remains lit but main burner drops out - usually low thermopile voltage reaching the valve.
Likely causes
- Pilot flame too small or not engulfing the thermopile
- Thermopile shorting / dirty connection
- Wall switch wire too long or too thin (too much resistance)
- Faulty thermostat or wall switch
Check in this order
- Turn up the pilot flame; if the flame pattern still does not engulf the thermopile, replace the pilot assembly.
- Clean the thermopile connections at the valve and reconnect.
- Check wall switch / thermostat wire run against max lengths: 14 ga 100 ft, 16 ga 60 ft, 18 ga 40 ft (2-strand solid-core millivolt wire). Shorten the run or use heavier wire.
- Replace the thermostat or switch if faulty.
- If still failing, replace the thermopile, then the valve.
Applies to: Napoleon GD70 STARfire direct-vent fireplace (GD70NT-S natural gas, GD70PT-S propane)
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Source: Napoleon GD70NT-S / GD70PT-S Installation & Operating Instructions W415-0434, Troubleshooting table, p.26; wire table from Gas Installation section. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.