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The customer was looking at the knob. The oven on their Wolf gas range had stopped lighting, and the knob was the visible control surface — twist it, the oven should light, that is the user-facing logic. When the oven didn’t light, the knob seemed like the obvious culprit.
It wasn’t the knob. The knob was working.
What had failed sat further down the ignition chain — and on a Wolf gas oven, that chain has more steps than the user-facing controls suggest.
The hot surface igniter is the part nobody thinks about first
Wolf gas ovens light through a hot surface igniter, not a spark electrode. The user request from the knob energizes the igniter, which heats up to a temperature that triggers the gas valve to open; gas flows past the now-glowing igniter and lights against it. There are at least three components in that chain — igniter, valve, thermostat — and any one of them can produce a non-lighting oven from the same user-facing symptom.
Hot surface igniters fail in a specific way that is easy to read on the multimeter. They accumulate resistance over their service life. As resistance climbs, current draw rises but heat output falls — the igniter pulls more amperage than it should but heats up more slowly and never reaches the temperature at which the gas valve is supposed to open. The cycle attempts. The igniter glows. The valve never opens. The oven never lights.
The igniter on this Wolf was reading well outside spec on resistance and was failing to reach valve-trigger temperature within the cycle window. End-of-life igniter, by definition.
The thermostat was failing in parallel
Hot surface igniters work in conjunction with the oven thermostat. The thermostat reads cavity temperature, compares it to setpoint, and drives the cycle that powers the igniter on demand. If the thermostat is no longer holding calibration against the cavity curve, the cycle does not behave correctly even when the igniter is healthy — the oven might overshoot, undershoot, fail to restart after the first heat cycle, or refuse to ignite cold.
Calibration testing against the cavity probe showed the thermostat had drifted out of spec. With both components compromised, lighting was inconsistent and temperature hold would have been unreliable even if lighting succeeded. Replacing only one of the two would have left the unit in a degraded state.
The fix
TechVill technician Leonid replaced both:
- Bake igniter (part #813541) — hot surface igniter that heats up on user demand to the temperature at which the gas valve opens
- Oven thermostat (part #815506) — temperature sensor and control that maintains cavity temperature against setpoint
After installation, the new igniter reached operating temperature inside its expected window, the gas valve opened cleanly on the trigger, and the burner lit on the first attempt of the test cycle. Cavity temperature held against setpoint through repeated cycle-on and cycle-off events. The bake control switch — the knob the customer had originally suspected — was confirmed operating correctly through the same testing.
Replacing them together rather than sequentially is the right call when both fail in parallel. A two-visit repair against the same fault chain is something that gets avoided by reading the chain end-to-end before deciding which parts to order.