Oven Not Heating: What a Technician Tests, Electric and Gas

An oven that will not heat, or heats far too slowly, has a fault somewhere in a short chain: power to the range, the control that calls for heat, the element or burner that makes it, and the sensor that tells the control when to stop. Electric and gas ovens share the control and the sensor and differ in everything else. A technician starts with the symptom, because “stove works, oven does not” already rules out half the chain, and then measures each part against the tech sheet. Below is that process, with the readings we expect on common Whirlpool, GE, Frigidaire, Samsung and LG ranges. Several of these tests are live, on 240 volts or with gas flowing.

The two most common versions of this call are an electric oven where the cooktop burners still work, and a gas oven where the top burners light and the oven does not. Both point inside the oven circuit, and both are covered below.

What a technician brings to this call

• A digital multimeter rated CAT III for 300 V or more, and a non-contact voltage tester.
• A clamp meter that reads AC amps down to a fraction of an amp, for the gas igniter test.
• An oven thermometer or a thermocouple probe that reads the cavity over a full heating cycle.
• Leak-detection solution and wrenches for the gas connector on gas ranges.
• Nut drivers and Torx bits, and the tech sheet, usually tucked behind the kick drawer, under the cooktop or in a pocket on the back panel. It lists sensor charts, element ratings, fault codes and the service test.

Read the symptom and the code first

What the oven does narrows the search before any meter comes out.

Codes on electronic ranges name a circuit. GE uses F3 and F4 for an open or shorted oven sensor. Whirlpool and Maytag codes in the F3 family point at the oven sensor circuit. Many Frigidaire ranges report F30 and F31 for an open or shorted sensor and F10 for a runaway temperature. Samsung and LG use their own code sets, listed on the tech sheet for the model. A sensor code with a good sensor sends the technician to the harness and the board connector. For GE Profile codes in detail, see GE Profile oven F codes.

Step 1: electric range, confirm 240 volts

A range’s elements run across both legs of the supply, L1 and L2, at 240 volts. The clock, lights and control run on 120 volts from one leg to neutral. When one leg drops, from a tripped half of the breaker, a burned terminal on the block or a damaged cord, the display stays lit and nothing heats properly.

With the range powered and the terminal block cover off at the back, the technician reads L1 to L2 (about 240 V in a house, about 208 V in many condo buildings with three-phase service), and each leg to neutral (about 120 V). A missing leg is a supply problem. Brown or melted plastic at the block means a loose connection that overheated, and the block and the cord end get replaced. On 208 V service, an element made for 240 V puts out roughly a quarter less heat, so the oven preheats slower and nothing is broken.

Step 2: electric oven, the elements and the sensor with power off

Turn off the breaker and confirm with the non-contact tester that the range is dead. Take the wires off each part before measuring so the meter reads only that part.

A bake element that has failed often shows it: a blister, a split sheath, or a spot that glowed white before it burned through. Many newer ranges hide the bake element under the oven floor, so there is nothing to see, and the floor or the rear panel has to come off to reach the terminals. The 1,080 to 1,100 Ω sensor value is typical of the common platinum sensors on Whirlpool, GE and Frigidaire. Some brands use different sensors entirely. Wolf, for example, uses its own RTD with its own curve, so the number comes from the sheet for that model.

A good resistance does not clear a part. An element can read correctly cold and open once it expands. A sensor can read within range at room temperature and drift at 350°F, which shows up as an oven that runs 40 degrees hot or cold. The sensor chart on the tech sheet lists values at several temperatures for that reason.

Step 3: electric oven, the control’s output under load

If the element, sensor and fuse are good, the control board may not be closing the relay that sends power to the element. The test is to set the oven to bake, and with the back panel off, read voltage across the bake element terminals or at the board’s relay output. About 240 V at the element with no heat means the element. No voltage while the control calls for bake means the relay, the board, or the wiring between them.

Boards fail for real reasons. The self-clean cycle runs the cavity around 880°F, and the heat that leaks into the control area during that cycle is one of the most common causes of board and fuse failures. Storm surges also take out relays on the board. Before replacing a board, the technician checks the harness and the connectors at the board for scorching, because a loose connector burns the relay terminal next to it.

Step 4: gas oven, the igniter and the safety valve

Most gas ovens built in the last few decades use a hot-surface igniter, sometimes called a glow bar, wired in series with the oven safety valve. When the control calls for heat, current flows through the igniter and through a small heater inside the valve. As the igniter heats up, its resistance drops and the current rises. When the current reaches the valve’s opening threshold, the valve opens, gas flows over the glowing igniter, and the burner lights.

That series arrangement is why a weak igniter is the most common gas oven failure. An igniter wears with age, its resistance rises, and it no longer passes enough current to open the valve. It still glows bright orange, which is why owners and many parts sellers assume it works. The test is current, not light:

A healthy oven igniter usually lights the burner within about a minute of the call for heat. An igniter that takes several minutes, or lights the burner with a soft whoomp, is letting gas collect before it lights, which is both a failure sign and a hazard. Gas ranges with a broil burner at the top of the cavity use a second igniter and valve circuit for broil, so broil working and bake failing points at the bake igniter.

Some ranges, older ones and some lower-cost models, use spark ignition with a flame sensor in the oven. Those are diagnosed differently, by the spark module, the electrode gap and the flame rectification signal, from the tech sheet for that model.

Step 5: temperature accuracy and calibration

An oven that heats but cooks badly is a different call from one that does not heat at all, and it is often fixed without parts. A technician never trusts one reading. Ovens cycle the element or burner on and off around the set point, and the cavity swings above and below the setting by 20 to 30 degrees on many models as part of normal operation. The test is a probe in the center of the cavity, read every minute or so over three or four heating cycles after preheat, averaged.

If the average is off by more than about 25 degrees with a sensor that reads correctly on the chart, most Whirlpool, GE and Frigidaire controls allow an offset of about 30 to 35°F either way through a button sequence in the manual. If it is further off than that, or swings wider than normal, the sensor, a door gasket letting heat out, or a gas burner running on the wrong orifice for the gas type is the suspect. For the Wolf version of this problem, see Wolf double oven thermostat replacement.

Reassembly and the test that confirms it

• Element terminals get new screws or nuts if the old ones are discolored, and the wire ends are cleaned or replaced. A loose element terminal arcs and burns the new element out at the same spot.
• The element’s mounting screws and any heat shield go back exactly where they were, so the element cannot contact the cavity wall.
• On gas ranges the igniter is mounted in its original position relative to the burner ports. An igniter mounted slightly off can glow and still fail to light the burner.
• The leak test on every gas joint touched, and the anti-tip bracket engaged before the range goes back against the wall.
• The confirming test is a full preheat to 350°F timed against the spec in the manual, then several cycles with a probe in the cavity to confirm temperature control.

What our technician does on an oven no-heat call, and what it costs

Symptom and code, 240 volts at the terminal block on electric ranges, element and sensor resistance against the tech sheet, board output under load, igniter amp draw and valve continuity on gas ranges, then a timed preheat and temperature check. Typical South Florida prices with parts and labor, from our current price pages:

• Electric oven not heating, bake element or sensor: $170 to $310
• Gas oven igniter: $220 to $310 on most ranges
• Oven safety valve: $220 to $400
• Oven temperature sensor: $150 to $280
• Temperature off or uneven baking, sensor or calibration: $180 to $360
• Control board or surge-damaged thermal fuse: $240 to $480

We repair every range and wall oven brand across Miami-Dade, Broward and Palm Beach, seven days a week. The service call is $59 and it is credited to the repair when you go ahead. Call (754) 345-4515, or see oven repair, range repair and gas stove repair. Brand pages: Whirlpool, GE, Samsung, LG. If the range is old and you are weighing a new one, read repair or replace a range or oven first.

Questions owners ask