1 steady flash = Normal operation. The gas valve LED flashing once at regular intervals means the unit is functioning normally and has no fault to report. This is the "good" indicator pattern.
What 1 flash actually means
- Pilot is lit (standing pilot units) or electronic ignition is ready
- Gas valve is in standby waiting for thermostat call
- No safety circuits have tripped
- FVIR sensor (if equipped) is normal
If you see 1 flash but the unit isn't producing hot water
- Check thermostat setting on the gas control valve — set to 120°F or "C"
- Check that gas supply valve to the unit is fully open
- Test another hot tap to verify no air-lock
- If electric supplemental (combo units): check breaker
Bottom line
1 flash = normal. If you're not getting hot water despite 1-flash status, the issue is downstream (cold supply, mixing, plumbing) rather than at the heater itself.