My Heat Pump Won't Turn On At All: What to Do
In most cases, a heat pump that won't turn on comes down to something simple you can check yourself: a tripped breaker, an outdoor disconnect switch left open, or a thermostat that's misconfigured or has a dead battery. This usually isn't dangerous. But if nothing works after these basic checks and it's your only heat source in extreme cold, don't put it off until tomorrow — get it inspected the same day.
What's Happening?
A heat pump needs three things to start: continuous power reaching the outdoor unit, a signal from the thermostat telling it to run, and no internal safety lockout active. If any one link in that chain is missing, the unit stays completely silent — no hum, no fan, nothing.
That's different from an abnormal noise or reduced performance: here, the unit simply doesn't respond at all, which almost always points to the power supply or thermostat communication rather than a worn internal mechanical part.
The good news: most causes can be checked in a few minutes, no tools needed, before you even think about calling anyone.
Is It Dangerous?
For your immediate safety, no — a heat pump that won't start isn't a fire or shock risk on its own. The real danger is prolonged heat loss in the middle of a Quebec winter.
Inspect or act quickly if:
- It's your only heat source and the indoor temperature is starting to drop
- The breaker trips again immediately after you reset it once
- You smell burning or hot plastic near the indoor or outdoor unit
- You'll be away for several days with nobody able to monitor the home's temperature (pipe-freezing risk)
- A vulnerable person (infant, elderly) lives in the home
A breaker that trips again on the first reset signals a real electrical fault — don't reset it a second time, call a professional instead.
Most Common Causes
| Cause | Explanation |
|---|---|
| Tripped breaker | The most common cause; often triggered by a momentary overload or a current spike at startup |
| Outdoor disconnect switch open or iced over | This small switch near the outdoor unit cuts power if it's in the "off" position or blocked by ice |
| Thermostat misconfigured, off, or dead battery | A wireless thermostat that loses power no longer sends any signal to the unit |
| Partial power outage in the home | A single circuit can be affected without the rest of the house seeming affected |
| Safety lockout after a compressor overload | The unit protects itself if it detected an issue during a previous cycle |
| Loose wiring between the thermostat and the unit | Common after recent electrical work or a renovation |
| Faulty control board or sensor | The electronic part managing the unit's internal signals; rarer, but possible |
Why This Happens in Quebec
Sudden extreme cold makes the compressor work harder at startup, which can trip a breaker already strained by other appliances on the same circuit — a classic scenario during the season's first cold snaps. The outdoor disconnect switch, exposed to the weather, also easily collects ice or wet snow after a storm, which can keep it from staying in the closed position.
Ice storms and high-wind power outages, common in rural areas, sometimes leave a single circuit without power even after the rest of the house is back on. And in older homes where the electrical panel is already loaded (heat pump, baseboard heaters, major appliances), a simultaneous current spike is sometimes enough to trip the breaker dedicated to the heat pump.
How to Check It Yourself
In order, no tools needed:
- Go to the electrical panel and look for a breaker sitting in a middle position (neither fully "on" nor fully "off"); reset it once
- Check the disconnect switch near the outdoor unit: it should be in the closed position, clear of snow or ice
- Check that the thermostat powers on, shows the correct time, and is set to heat mode (not "off")
- If the thermostat is wireless, swap the batteries to rule out this simple cause
- Check whether other devices on the same circuit are working, to confirm whether the outage is isolated to the heat pump
What you should never do yourself: open the outdoor unit's control box, touch the wiring inside, or reset a breaker that keeps tripping. A breaker that trips again is protecting against a real short circuit — forcing it can create a fire risk.
Can I Ignore It?
It depends on the season and your situation. In shoulder season, with another heat source available, you can wait for a regular appointment without issue. In the middle of winter, if it's your only heat source, no — a home can lose several degrees per hour in extreme cold, and water pipes start to risk freezing after several hours without heat, especially in less-insulated areas like a basement or crawl space.
How Much Does It Cost?
| Service | Estimated Price |
|---|---|
| Diagnostic visit | $100 - $150 |
| Electrical repair (breaker, disconnect, wiring) | $150 - $400 |
| Control board or sensor replacement | $300 - $700 |
| Compressor replacement | $1,500 - $3,000 |
| Full heat pump replacement | $4,000 - $12,000 |
When to Call a Professional
- The breaker trips again immediately after a single reset
- Nothing happens even after checking the breaker, the outdoor disconnect, and the thermostat
- It's your only heat source and the unit stays down for more than a few hours in cold weather
- You smell burning or see visible damage on the unit
- The problem keeps recurring even after a recent repair
A certified technician can test the electrical circuit, the control board, and the compressor with tools you don't have at home, and identify the exact cause in a single visit instead of guessing.
Related Questions
- My Heat Pump Is Making a Clicking or Grinding Noise: Is It Serious?
- Why Does My Heat Pump Make a Repeated Clicking Sound Right Before It Starts?
- My Heat Pump Is Covered in Frost or Ice in Winter: Is That Normal?
- How Long Should I Really Wait After Turning My Heat Pump Off and Back On?
- Who Do I Call If My Breaker Trips Every Time My Heat Pump Starts: an Electrician or an HVAC Technician?
- When to Replace Your Heat Pump: 7 Signs to Watch For
- Spring Heat Pump Maintenance Checklist
- Why Did One of My Outlets Suddenly Stop Working?
Frequently asked questions
Can I reset the breaker more than once to see if it works?+
No. Reset it once only. If it trips again right away, that's a sign of a real short circuit or overload — resetting it repeatedly can create a fire risk instead of fixing the problem.
How long before my pipes risk freezing if the heat is off in winter?+
It varies with outdoor temperature and insulation, but the risk becomes real after several hours without heat in extreme cold, especially in a basement or near a poorly insulated exterior wall. Don't take chances if it's your only heat source.
Should I call an electrician or an HVAC technician?+
If the breaker keeps tripping repeatedly, an electrician can confirm whether it's a panel or circuit issue. For anything involving the unit itself (control board, compressor), a certified HVAC technician is the right call.
Can a completely blank thermostat display really be the only cause?+
Yes, more often than you'd think. A wireless thermostat with a dead battery stops sending any signal to the unit, which then stays silent even though it's fully powered. Swapping the batteries fixes it in a good number of cases.
Do I need to call a professional right away?+
Not if you haven't yet checked the breaker, the outdoor disconnect, and the thermostat — those checks resolve most cases within minutes. Call promptly if none of that works, especially in extreme cold.
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By Marc Tremblay — Certified HVAC technician, 12 years of experience in Quebec
Updated on July 24, 2026