Nobody calls about an oven until something they cared about comes out wrong. A roast forgives fifty degrees. A cake forgives about ten. So the complaint almost always arrives as baking, and the first thing worth knowing is that most people reporting a fifty-degree error have never measured one.
Measure it before anyone quotes you
Put a dial or probe thermometer on the centre rack. Set 350°F. Leave it a full twenty-five minutes — an oven that has "preheated" has only reached temperature at the sensor, not settled its cycling — then read it every five minutes for another fifteen and write the numbers down.
What those numbers mean:
- •Steady, but off by 15 to 40 degrees. Calibration. Nearly every oven built since the mid-nineties has an offset adjustment buried in the control settings, and it is a free fix you can do yourself with the manual open.
- •Readings that yo-yo by 40 degrees or more around what you set. Not calibration. The control is being lied to, or the heat source is cycling wrong.
- •Climbs, then stalls well short. Element, igniter or a relay on the control board.
- •Perfect on the thermometer, wrong in the food. Look at the fan and the door seal before the electronics.
That sheet of numbers is worth more to whoever comes out than any description of how the cookies looked.
Gas is the default here, and the igniter is the trap
Greater Boston runs on gas to a degree that surprises people who move here from newer housing markets. Triple-deckers, brownstones, three-families in Southie and Dorchester, most of the rental stock inside 128 — gas ranges throughout, many of them well past twenty years old.
The ignition sequence on a gas oven matters because misreading it is the most expensive wrong conclusion in this trade. The igniter glows. As it heats, its resistance falls and the current through it rises. The gas safety valve is a bimetal device that opens only when that current crosses a threshold — usually somewhere around 3.2 to 3.6 amps depending on the valve.
Igniters age by losing current draw while still glowing perfectly brightly. So the homeowner sees a bright orange element, concludes the igniter is obviously fine, and asks us to price a gas valve. In the overwhelming majority of cases it is the igniter. If your oven glows for ninety seconds and then simply gives up without lighting, that is the classic weak-igniter signature.
We meter it in series rather than judging it by eye, because the difference between those two parts is several hundred dollars and the eye cannot tell them apart.
Electric: element, or the relay that feeds it
A dead bake element often shows itself — a visible break, a blister, a bright arc scar. But elements also fail while looking completely intact, and the control board relay that switches them can weld shut or fail open with the element in perfect condition. Those two faults are identical from the kitchen side and differ by a couple of hundred dollars, so they get metered, not guessed.
One free diagnostic: on most electric ovens the broil element handles the top of the cavity independently. An oven that broils happily but will not bake has already told you which circuit to look at.
The sensor, and what 1,080 ohms means
Almost every modern oven senses cavity temperature with an RTD — a resistance probe at the back wall that reads close to 1,080 ohms at room temperature and climbs as the oven heats. When it drifts high, the control believes the oven is hotter than it is, shuts the heat off early, and everything comes out pale. It is a cheap part and a fast job. The diagnosis is the whole value.
Self-clean, and the repair calls that follow it
We can nearly set a calendar by this. The week before Thanksgiving, people run self-clean for the first time in a year, and the following week we get the calls.
Pyrolytic cleaning takes the cavity to 850–900°F, far above anything in normal cooking. On a range that is fifteen or twenty years old — which describes a large share of what is installed in this city — that is the single most common trigger for a thermal cutout opening permanently or a control board failing outright. The oven cleans beautifully and then never heats again.
If your oven died during or just after a self-clean, say so when you book. It points straight at the thermal fuse and the board and saves us an hour. And on any older range, our honest advice is to clean it by hand, or use the low-temperature steam option if the model has one.
Professional ranges are a different conversation
The renovated kitchens in Newton, Brookline, Wellesley, Lexington and the Back Bay have brought in a lot of Wolf, Viking, Thermador and BlueStar. These are worth repairing well past the point where a freestanding range would be replaced — the burners, igniters and valves are serviceable individually, and the carcass outlives several rounds of parts.
They also carry their own quirks: infrared broilers with dedicated igniters, dual-fuel models where the electric oven and gas cooktop fail entirely independently, and parts that are ordered rather than stocked. We will tell you which of those you are dealing with before we come out.
What decides the figure
Sensors, igniters and bake elements are modest parts and the labour on them is straightforward. Control boards are the step up, and professional ranges sit above both — bigger parts, longer access, and components ordered rather than stocked.
Which of those you are looking at is established at the diagnosis, and you approve one number covering parts and labour before anything is dismantled. What we will not do is put a figure on it beforehand, because the three possibilities above are not comparable and a number guessed over the phone is not an estimate.