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Commercial Commercial Range & Oven: Oven Won't Heat — Causes & Fixes

Compiled by Resultex Media Group · Editorially reviewed · Last verified August 2026

Quick answer: First relight the oven pilot per your manual and confirm the range's manual gas valve is open — a gas oven with a standing pilot and safety valve simply won't fire if the pilot is out, because the safety valve then shuts off gas to the oven burner. Follow the lighting steps exactly: thermostat OFF, open the kick panel, hold the safety-valve button in while lighting the pilot, keep holding ~30 seconds, then release; the pilot should stay lit. If the pilot lights and stays lit but the oven burner still won't come on when you turn up the thermostat, or the pilot won't stay lit, stop — the fault is in the thermocouple/thermopile, safety valve, or thermostat, which are technician parts. On a convection oven, also confirm the blower and electrical supply are on.
Food safety: An oven that isn't reaching temperature will not cook food to safe internal temperatures. Use a probe thermometer to verify doneness (FDA Food Code 3-401.11) and discard, rather than serve, any product that did not reach its required temperature. Do not hold potentially hazardous food in the 41°F–135°F danger zone while the oven is down. Note: returning food to 41°F does not by itself make it safe. If the time/temperature history is unknown, segregate the product and follow your food-safety plan; the FDA Food Code’s time-as-a-public-health-control provisions require specific written procedures, and local health-department requirements may differ. When safety cannot be verified, discard it.

Check in this order (5-minute diagnostic)

Work top to bottom — the quickest, most-likely checks are first.

  1. Oven pilot is out / needs relighting. Look through the opening in the oven bottom for a lit pilot. If it is out, the safety valve has shut off gas to the oven burner.
  2. Manual gas valve off or (convection) power/blower off. Confirm the range's manual gas shut-off valve is open. On a convection oven, confirm the unit is plugged in, the breaker is on, and the fan/blower switch is on — the blower must run for proper operation.
  3. Weak thermocouple / thermopile can't hold the safety valve open. The pilot lights and stays lit while you hold the button, but drops out when you release it, or the pilot stays lit yet the oven burner never fires. The thermocouple/thermopile senses the pilot and holds the safety valve open; Southbend's flowchart calls for a thermopile reading above 450 millivolts.
  4. Failed safety valve or oven thermostat. The pilot and thermopile are good (thermopile above ~450 mV) but the oven still won't fire, or turning the thermostat up does not make the pilot flame grow. That points to the safety valve or the oven thermostat/valve.
  5. Clogged pilot orifice, draft, or air in the gas line. The pilot won't light or won't stay lit even after several tries. Causes include a dirty/clogged pilot orifice, a draft from an over-strong exhaust fan, poor ventilation, or air in the line after the gas was off.

Likely causes, checks & fixes

Likely causeHow to checkWhat to doWho
Oven pilot is out / needs relightingLook through the opening in the oven bottom for a lit pilot. If it is out, the safety valve has shut off gas to the oven burner.Relight the oven pilot following the manual: turn the thermostat OFF, open the louvered kick panel, depress the safety-valve button while applying a flame to the pilot, hold at least 30 seconds, release (the pilot should remain lit), then set the thermostat. If it won't light or won't stay lit, see the causes below.Basic
Manual gas valve off or (convection) power/blower offConfirm the range's manual gas shut-off valve is open. On a convection oven, confirm the unit is plugged in, the breaker is on, and the fan/blower switch is on — the blower must run for proper operation.Open the manual gas valve; for convection models turn on the electrical supply and the blower switch. Note: in a power failure a convection range should not be operated.Basic
Weak thermocouple / thermopile can't hold the safety valve openThe pilot lights and stays lit while you hold the button, but drops out when you release it, or the pilot stays lit yet the oven burner never fires. The thermocouple/thermopile senses the pilot and holds the safety valve open; Southbend's flowchart calls for a thermopile reading above 450 millivolts.Call a qualified gas service technician to test the thermopile output and clean or replace it. This is a gas-carrying safety part and is not owner-serviceable.Technician
Failed safety valve or oven thermostatThe pilot and thermopile are good (thermopile above ~450 mV) but the oven still won't fire, or turning the thermostat up does not make the pilot flame grow. That points to the safety valve or the oven thermostat/valve.Have a qualified technician test and replace the safety valve or thermostat. Do not bridge or bypass the oven safety valve.Technician
Clogged pilot orifice, draft, or air in the gas lineThe pilot won't light or won't stay lit even after several tries. Causes include a dirty/clogged pilot orifice, a draft from an over-strong exhaust fan, poor ventilation, or air in the line after the gas was off.After the gas has been off, light the oven first and purge air per the manual before expecting a steady pilot. Reduce excessive drafts. Cleaning the pilot orifice and the safety-valve circuit is a technician task — call a qualified servicer if the pilot still won't hold.Technician

Who can do it: DIY-safe owner-doable · Basic simple part swap · Technician refrigerant/gas/electrical — call a licensed pro.

How to do the safe fixes

Owner-doable procedures only. Anything on the "Technician" list above needs a licensed pro.

Relight an oven standing pilot (per manual) DIY-safe
  1. Turn the oven thermostat to OFF (and on a convection oven, the fan switch to OFF). Confirm the range's manual gas valve is on.
  2. Open the louvered kick panel below the oven door (lift slightly and rotate the top edge outward / down 90°) to reach the safety valve and pilot.
  3. Depress and hold the button on the oven safety valve while applying a flame to the pilot through the opening in the burner-box area.
  4. Keep the button held in for at least 30 seconds after the pilot lights so the thermocouple heats up; the pilot flame should be large enough to reach the thermocouple tip.
  5. Release the button — the pilot should stay lit. If it goes out, turn the control OFF, wait 5 minutes, and repeat. Never try to relight without waiting 5 minutes.
  6. Return the kick panel to its position, turn on the convection fan switch if applicable, then set the thermostat. If the pilot still won't stay lit, stop and call a qualified gas technician (dirty orifice, weak thermocouple, or bad safety valve).

· Tools: Long match or long-reach lighter, Flashlight (to confirm the pilot) · Source: Wolf Challenger XL Manual (Oven Section lighting); Southbend S Series (Operation of Gas Oven)

Clean clogged open-top burner ports DIY-safe
  1. Turn the burner and its pilot OFF and let everything cool completely; shut off the gas to the burner if you will lift it out.
  2. Lift out the grate and, on open-top models, remove the burner from its support bracket.
  3. Brush carbon and food debris off the burner and clear each port so it is open; clean the venturi tube and the air mixer of lint and debris. Do not enlarge or reshape the ports.
  4. Clean around the pilot area and under the burner (a wire brush is fine). Wash the grate in hot soapy water, rinse, and dry quickly to avoid rust.
  5. Let the burner drain and dry thoroughly, then reinstall it level in its bracket, aligned with its valve/orifice.
  6. Relight the pilot and turn the burner on; confirm a steady blue flame on every port. If the flame is yellow or lifts off the ports, have the air shutter set by a trained person.

· Tools: Stiff wire brush, Straightened wire or a stiff bristle brush for the ports, Mild detergent and hot water · Source: Southbend S Series (Cleaning — Top Burners; Troubleshooting Open-Top Burners); Garland commercial range troubleshooting (Parts Town)

Check gas oven thermostat calibration against a thermometer Basic
  1. Put an accurate thermometer in the geometric center of the oven with the oven bottom in place (and, on a convection oven, the blower baffle in place and the fan on).
  2. Light the oven, set the thermostat to a known temperature (Southbend uses 350°F; Garland uses 400°F), and let it heat for about 15 minutes / until it has cycled a few times.
  3. Read the temperature over several burner cycles, opening the door as briefly as possible; the true oven temperature is the midpoint between the low and high 'swing' readings.
  4. Compare to the dial. Recalibrate only if it is outside tolerance (Southbend: not within 20°F of 350°F; Garland: within ±20°F at 400°F).
  5. On a mechanical-dial control you may follow the manual's calibration (e.g., Southbend: insert a screwdriver through the center of the thermostat stem and turn the adjustment screw in small steps — clockwise to lower, counterclockwise to raise — rechecking each time). Do not open the gas valve, burner, or wiring to 'adjust' temperature.
  6. If the control won't come into tolerance, a second setpoint is also off, or the control is electronic, stop and have a technician replace the thermostat/sensing element.

· Tools: Accurate oven thermometer or test instrument, Flat screwdriver (only if your manual's dial adjustment calls for it) · Source: Southbend S Series (Calibration of Gas Oven Thermostat); Garland service manual (thermostat calibration at 400°F)

Stop and call a qualified technician if:
Repair or replace? A gasket, coil cleaning, or a simple part is almost always worth fixing. Weigh replacement when the unit needs a compressor or sealed-system repair and is roughly 8–10+ years old, or when repeated service calls approach the cost of a new unit. Compare current commercial range & ovens →

Related commercial range & oven problems

Frequently asked questions

Why is my commercial range & oven oven won't heat?

First relight the oven pilot per your manual and confirm the range's manual gas valve is open — a gas oven with a standing pilot and safety valve simply won't fire if the pilot is out, because the safety valve then shuts off gas to the oven burner. Follow the lighting steps exactly: thermostat OFF, open the kick panel, hold the safety-valve button in while lighting the pilot, keep holding ~30 seconds, then release; the pilot should stay lit. If the pilot lights and stays lit but the oven burner still won't come on when you turn up the thermostat, or the pilot won't stay lit, stop — the fault is in the thermocouple/thermopile, safety valve, or thermostat, which are technician parts. On a convection oven, also confirm the blower and electrical supply are on.

When should I call a technician instead of fixing it myself?

Call a licensed technician for anything involving the sealed system, refrigerant, gas, or high-voltage wiring — for example: Weak thermocouple / thermopile can't hold the safety valve open; Failed safety valve or oven thermostat; Clogged pilot orifice, draft, or air in the gas line. These are diagnostic-only for an operator.

Is it worth repairing or replacing?

Simple fixes (gaskets, coil cleaning, a single part) are worth repairing. Consider replacing when it needs a compressor or sealed-system repair and is 8–10+ years old, or when repeat service calls near the price of a new unit.

Sources