A Navien tankless unit installed in a Rockwall home in late 2025 had started throwing recurring Error 003 — ignition failure. The homeowner had been resetting the unit each time it errored, which restored operation temporarily before the fault returned.
On inspection, the gas shut-off valve was found partially closed. Restricted gas flow was preventing the unit from achieving ignition reliably, triggering the error each time demand exceeded what the partial supply could sustain. The valve was fully opened and the unit ran hot water continuously at the dishwasher with no error codes.
As a precaution, the flame rods were pulled and sanded down to rule out any secondary ignition issue. Unit confirmed running clean before leaving.
Ignition errors on tankless units aren’t always a unit fault — gas supply, venting, and flame rod condition all play a role. For Navien repairs or any water heater issue in Rockwall, our local team handles diagnostics and repairs. See our water heater repair services.
