Thermocouple Replacement · Bellevue · Eastside WA
Gas fireplace thermocouple replacement.
The thermocouple is the single most common cause of pilot light failure. Replacement is a quick repair — usually same-day. We carry common parts on the truck.
Most common repair
Thermocouple vs. thermopile — what's the difference?
These two components do similar jobs but aren't the same. Knowing which one your fireplace uses helps us come prepared with the right part on the first visit.
Thermocouple
Generates a small millivolt signal (around 25-35 mV) that holds the pilot gas valve open. Used in fireplaces where the pilot assembly is completely independent — you light the pilot manually and it holds itself open. Failure: pilot lights but goes out after 30-60 seconds.
Typical output: 25–35 mV. Minimum needed: ~18 mV.
Thermopile
Generates a larger voltage (around 300-750 mV) that powers the gas valve and sometimes a wall switch or thermostat. Used in fireplaces where you control the flame height from a switch or remote. Failure: fireplace won't respond to the switch or shuts off randomly.
Typical output: 300–750 mV. Minimum needed: ~150 mV.
The Symptom Pattern
Pilot Lights, Then Goes Out — That's the Tell
The classic thermocouple failure symptom: you hold the pilot button, light the pilot, count to 30... and the moment you release the button, the pilot goes out. That happens because the thermocouple needs to heat up enough to generate the signal that holds the gas valve open. If output is too low, the valve doesn't stay open.
Sometimes it's gradual — the pilot used to hold fine but now it goes out faster and faster. That's the thermocouple weakening over time. When output drops below the valve's threshold, it stops holding.
Got Questions?
Frequently Asked Questions
Describe your symptoms — pilot behavior tells us a lot before we even arrive.
Fix It Today
Same-Day Thermocouple Replacement
We stock parts for most major brands. Call or text — we'll get it sorted fast.