A burner that runs at full power regardless of where the knob sits, or that will not switch off at all, is one of the few appliance faults worth treating as urgent rather than annoying. Almost always the cause is a set of switch contacts that have welded themselves closed — the infinite switch on a coil or radiant cooktop, or a relay on the control board of an electronically controlled one. Both are repairable. Neither is safe to live with, so the very first action is to isolate the range at the breaker.
Read this first
- A burner you cannot switch off is a fire hazard. Switch the range off at the breaker now and leave it off until the fault is fixed. Do not rely on the knob.
- Verify the circuit is dead with a meter before touching anything behind the control panel. An electric range runs on 240 volts.
- Let the element and the cooktop cool completely. A radiant element under glass holds heat long after it looks off.
- Do not put anything on top of the cooktop while the breaker is off as a reminder — put tape over the knob instead, and tell everyone in the house.
- If you find scorched wiring, a melted connector, or a burnt smell behind the panel, stop and get an electrician.
Step by step
Isolate the range and mark it
Switch the range off at the breaker, not just at the knob, and put tape over the knob and a note on the panel so nobody switches it back on. Then confirm the burner is actually cold before doing anything else. This is not excessive caution: a burner stuck on high with no working control is a live heat source in a kitchen, and the whole diagnosis takes an hour or two during which somebody else in the house may well try to use the cooktop.
Establish exactly what the control does
With power restored briefly and someone watching, turn the affected knob through its full range and note the behaviour. Full power at every position with no cycling points at welded switch contacts. Full power even in the off position points at the same fault, more advanced. A knob that turns loosely with no effect at all points at a stripped knob or a broken switch shaft — a benign and cheap cause. Compare against a burner that works correctly, which should audibly click on and off at medium settings.
Check the knob and the switch shaft
Pull the knob off and look at the D-shaped or splined shaft it sits on, and at the corresponding socket inside the knob. Plastic knobs round out, and once the flat is stripped the knob turns freely while the switch stays exactly where it was — which on a burner last used on high leaves it on high. Try turning the shaft itself with pliers, gently, and see whether the burner responds. If it does, you have found the fault and a new knob is the whole repair.
Understand what an infinite switch does
The infinite switch is not a dimmer. It cycles the element fully on and fully off, varying the proportion of time it spends on, using a small internal bimetal heated by the current. That is why a correctly working burner clicks periodically at medium settings. When those contacts carry enough current for long enough they can weld shut, and once welded the element is permanently connected regardless of knob position. On both coil and radiant cooktops this is what the symptom describes almost by definition — an element permanently connected is what welded contacts do.
Test the infinite switch
With the breaker off and verified dead, get behind the control panel — usually by removing the rear panel or lifting the cooktop, depending on the design. Photograph the wiring before disconnecting anything. Disconnect the switch and test continuity between the line terminals and the element terminals with the knob in the off position: a good switch reads open. Continuity in the off position confirms welded contacts and condemns the switch. Note the switch's ratings and terminal layout when ordering, since they differ between positions on the same range.
Check the element for a short to the chassis
Less common but worth ruling out: a coil or radiant element whose internal conductor has shorted to its sheath can pass current to earth and heat continuously. With the element disconnected, measure resistance between each terminal and the element's metal sheath or bracket. A healthy element reads open to ground. Any measurable reading means the element is faulty and needs replacing — and that fault also tends to trip breakers, so if the range has been doing that too, this is likely your answer.
Look at the relay on an electronically controlled cooktop
Some smoothtop and most induction cooktops switch their elements with relays on a control board rather than a mechanical infinite switch. Relay contacts weld in exactly the same way, and the symptom is the same: an element that will not switch off, sometimes with the display insisting it is off. There is no user-serviceable repair here — the board is the part. Before ordering one, do a full power-down at the breaker for five minutes to rule out a hung control state, and check the board is still available for your model.
Inspect the receptacle and wiring while you are in there
On a coil range, look at the receptacle the element plugs into for burn marks, pitted contacts, or a melted housing, which is a common find on the burner people use most. On any range, check the terminals at the switch and the element for browning and for insulation that has hardened or cracked with heat. This does not usually cause a stuck-on burner, but it is a genuine hazard in its own right and you are unlikely to have the panel off again soon.
What this repair costs
Doing it yourself
$8–$100
Hiring a technician
$150–$600
Prices are general estimates for typical US jobs, not quotes. What you actually pay depends on your appliance's brand and age, the part required, your region, and each shop's labour rate. The DIY figure assumes you supply the labour and buy the part yourself.
Parts you may end up buying
| Part | Install | Typical price | Typical lifespan |
|---|---|---|---|
| Bake Element | easy | $15–$40 | 10–15 years |
| Oven Temperature Sensor | easy | $15–$30 | 10+ years |
| Broil Element | easy | $20–$75 | 10–15 years |
| Oven Igniter | moderate | $25–$90 | 5–10 years |
| Surface Burner Igniter | moderate | $20–$95 | 8–15 years |
| Radiant Surface Element | moderate | $25–$100 | 10–15 years |
| Infinite Switch | moderate | $20–$70 | 10–15 years |
| Oven Door Gasket | easy | $20–$80 | 8–15 years |
| Oven Door Hinges | moderate | $30–$120 | 10–15 years |
| Electronic Control Board | moderate | $90–$380 | 10–15 years |
Still not fixed
When to call a pro
Call a technician if the fault is on an electronically controlled or induction cooktop, since that is a board-level repair rather than a switch swap, and boards are neither cheap nor returnable once fitted. Call an electrician if you find scorched wiring, a melted receptacle, or damage at the range's supply connection. And if you are not equipped to verify a 240-volt circuit is dead before working behind the panel, that alone is a good reason to hand this over — but switch the range off at the breaker in the meantime rather than leaving it in service while you wait for an appointment.
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