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Electric baseboard heater won't shut off

A heater that won't quit is unsettling, but it's usually one failed part — most often the thermostat — and you can stop it safely right now by switching off its breaker.

tuneWhat are you noticing?
Select anything that matches and the checklist below reorders to fit. Not sure? Skip it.
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In Canada, the most common cause to rule out is a thermostat whose contacts have welded shut. Turn the dial or thermostat all the way down; if the heater keeps running full blast, the switch is no longer cutting power. It costs nothing to check, and you can stop the heater right now by switching off its breaker — but the repair is a live 240-volt thermostat swap, so read the safety note first.

Ranked from real-world failure data. The order updates as you select what you’re noticing above.

Likely causes, in the order to check them

Showing the typical order
Beginner-friendly Doable, with care Safety-critical Call a pro

visibilityHow to check

report This is a live 240-volt circuitBaseboard thermostats switch the full 240 volts, and both wires stay live even with the dial turned "off" — only the breaker truly de-energizes the heater. Kill the breaker before you open the thermostat and verify it's dead. If testing a live circuit isn't something you're set up to do safely, stop here: this is a fast, inexpensive job for a licensed electrician.
  1. With power still on, turn the dial or thermostat fully down (or to "off"). If the heater keeps running full blast, the switch is not opening — that alone is a strong sign the contacts are welded.
  2. Switch OFF the breaker for that circuit, verify the heater is dead with a voltage tester, then remove the thermostat cover — a line-voltage thermostat carries the full 240 volts.
  3. With power off, inspect the contacts for pitting or fused metal, and check continuity across the switch: a thermostat that reads closed (continuous) even in its "off" position has welded contacts and must be replaced.
buildmultimeterbuildscrewdriver schedule20 min

handymanHow to fix it

Stop it now — go to the electrical panel and switch off the breaker for that circuit so the heater stops drawing power, then keep drapes, furniture, and bedding well clear until it's repaired.

  1. At the electrical panel, find the breaker for that room's baseboard circuit — it may be labelled by room, or trace it by which breaker stops the heater.
  2. Switch it fully OFF. Confirm the heater has stopped and is cooling down.
  3. Pull drapes, furniture, and bedding well clear of the heater, and leave the breaker off until the thermostat or wiring is repaired.
schedule5 min savingsusually free
gavel Check your province first AB: homeowner may do this · BC: homeowner may do this · ON: homeowner may do this · PE: homeowner may do this · QC: homeowner may do this · AB: homeowner may do this · BC: homeowner may do this · ON: permit + inspection required · PE: homeowner may do this · QC: licensed professionals only
Switching a circuit off at your own panel is not electrical work — it's routine and permitted for any homeowner in every province.

handymanHow to fix it

On the thermostat screen, cancel any "Hold" or "Vacation" override and lower or reset the schedule so it stops calling for heat; if it's badly mis-programmed, do a factory reset and re-enter a sensible schedule.

  1. Look for a "Hold," "Permanent Hold," or "Vacation" indicator on the display and cancel it so the thermostat returns to its schedule.
  2. Lower the current setpoint below room temperature and confirm the heater switches off within a minute or two.
  3. Review the programmed schedule for a stuck-high period; if it's tangled, reset the thermostat to defaults and re-enter a simple schedule.
schedule10 min savingsusually free

verifiedWhy this one goes to a pro

If 240-volt line power is reaching the heater without passing through the thermostat, a wire has been mis-connected or has failed. Repairing it safely means finding why the thermostat is being bypassed, not just re-landing a wire. Leave the circuit off and have a licensed electrician trace and repair it.

Your notes travel with the request — what you saw, what you ruled out, when it started — so the pro arrives with a head start instead of a mystery.

warning If the wiring isn't clearly labelled, hand this to an electricianWorking out which thermostat controls which heater means opening 240-volt junctions with the breaker off and verified dead. If the wiring is unlabelled, shared between rooms, or you're unsure what feeds what, don't guess — a licensed electrician can map and correct it quickly and safely.
sort

Why the list is in this order

We don’t sort by likelihood alone. We sort the way a good, honest tradesperson thinks: rule out the free, safe, common causes first. That’s why the cheap checks outrank the expensive repairs — and why anything dangerous gets a hard stop instead of a pep talk. The order exists to save you money, not to sell you anything.