Gas Oven Igniter Glows But No Gas Only When Cold Decision Tree

Why this matters

A gas oven whose igniter glows brightly but will not light, and only when the oven is cold (first ignition of the day, then fine once warm), is a textbook weak-igniter case that techs frequently misread as a gas-valve or control fault. The bake safety valve is current-operated: it opens only when the igniter pulls enough amperage to heat its bimetal, typically 3.2 to 3.6 amps for a flat (Norton/Carborundum) igniter or 2.5 to 3.0 amps for a round (round/cylindrical) igniter. As an igniter ages it still glows orange but its resistance climbs, so it draws less current, and when the unit is cold the valve needs the most current to open. Once everything is warm the valve opens at slightly lower current and the unit lights, masking the fault. A tech who sees the glow and condemns the valve buys the wrong part. Measuring current in series is the only way to settle it.

Symptom presentation

The owner reports the oven failing to light on the first cold attempt, the igniter glowing for a minute or two without gas, then the unit lighting normally on a second try or later in the day once warm. Sometimes a delayed ignition produces a soft boom as accumulated gas lights late. The stovetop burners (separate spark ignition) work fine, confirming gas supply to the appliance. If the igniter does not glow at all, this tree does not apply; that is an open igniter or no power, diagnosed differently.

Quick checks

Confirm gas is on and the stovetop lights, proving supply pressure. Set the oven to bake and watch the igniter: a healthy glow that never produces flame is the signature. Note timing precisely, whether it lights on retry once warm. Smell for delayed-ignition gas accumulation and ventilate if present. With the oven cold, prepare to read igniter current in series, which is the definitive test; visual glow color is unreliable because a weak igniter still glows.

Isolation tree

Branch 1, igniter current draw, the primary test. Put a clamp meter around one igniter lead (or break the circuit and read in series) and start a cold ignition. Read the steady current once the igniter is fully hot. Flat igniter below about 3.2 amps, or round igniter below about 2.5 amps, means the igniter is weak: it will not reliably pull the valve open cold even though it glows. Replace the igniter. A weak igniter is by far the most common cause of this exact symptom.

Branch 2, safety valve. If the igniter draws correct current (flat at 3.6 to 4.0 amps, round at 2.9 to 3.3 amps) and the valve still does not open cold, the bake safety valve bimetal is weak or the valve is failing. Confirm by reading line voltage across the valve coil during the glow (should be present) and confirming correct current through the series circuit. With proper current present and no gas flow, replace the valve. Note this branch is reached only after current is confirmed good, the opposite of the common misdiagnosis order.

Branch 3, gas pressure and orifice. Low manifold pressure can leave the oven hard to light cold while the stovetop still works. Verify manifold pressure with a manometer against the rating plate (commonly about 3.5 in WC for natural gas, 10 in WC for LP; confirm by model). Inspect the oven orifice for blockage. Correct pressure or clear the orifice as needed.

Branch 4, wiring and connections. A high-resistance connector in the igniter circuit raises total resistance and lowers current, mimicking a weak igniter. After replacing an igniter that tests weak, verify the new one draws correct current; if it still reads low, inspect the harness and the oven control's bake relay contacts for resistance. The igniter circuit runs through the oven control's bake contacts and any in-line splice; a corroded porcelain wire nut at the igniter (a common high-heat failure point behind the rear panel) adds series resistance that starves current cold and explains why a brand-new igniter still will not light. Read voltage across each suspect connection under load; more than a few tenths of a volt dropped across a single connector points to it as the resistance source.

Confirming diagnosis

The series current reading is the arbiter. Glow without flame plus low current equals a weak igniter, full stop. Glow with correct current and no gas equals a failed safety valve. After replacing the igniter, re-measure current cold and confirm it lands in spec and the valve opens within seconds of full glow. Then perform several cold-start cycles, ideally after letting the oven cool fully, to prove the cold-only failure is gone.

Remediation

Replace the weak igniter with the correct flat or round OEM type; never substitute across types since the current ranges differ. Handle the new igniter only by its ceramic base, as skin oil and fingerprints on the silicon-carbide or silicon-nitride element cause hot-spot failure. After installation, verify current draw cold and confirm timely ignition with no delayed-light boom. If the valve was replaced, leak-check every joint disturbed.

References

• ANSI Z21.1 / CSA 1.1, Household Cooking Gas Appliances, ignition-system and safety-shutoff requirements.
• ANSI Z223.1 / NFPA 54, National Fuel Gas Code, supply pressure and leak-test provisions.
• Whirlpool/GE Gas Range Tech Sheet, igniter current-draw specifications (flat versus round) and safety-valve operation.
• DOE 10 CFR 430 Subpart B, gas oven test procedure and input-rate verification.