Why is my heat pump not working?
Ben Amina
Aire One East Heating & Cooling, 1910 Dundas St E #117, Whitby
A heat pump not working is a home heating and cooling system that fails to start, run, heat, or cool as set, and in a Durham Region February or a humid July that failure moves from annoying to urgent within hours. The good news is that a large share of these calls need no repair at all. This guide walks through the same sequence our technicians use, ordered from free checks to the faults that require a licensed heat pump service visit.
- The most common cause of a heat pump not working is not a broken heat pump. It is a thermostat on the wrong mode, a tripped breaker, or a clogged filter.
- Three checks take five minutes, cost nothing, and end many service calls: thermostat mode and batteries, breaker and disconnect switch, and the air filter.
- Ice on the coil, a breaker that trips twice, grinding sounds, or burning smells mean stop troubleshooting and call a licensed technician.
- Refrigerant work is never a DIY job. In Canada it legally requires certified handling under federal ozone protection rules.
- Typical single-component repairs in Durham Region run $250 to $600 CAD in 2026; compressors and reversing valves run higher and can push a 10+ year old unit into replacement territory.
Short answer: a heat pump not working is most often caused by a wrong thermostat mode, a tripped breaker, or a clogged air filter, and those three checks take about five minutes.
If the unit still will not run after those checks, or you see ice on the coil, stop there. Aire One East runs 24/7 heat pump diagnostics across Durham Region. Call 905-576-7600.
- Why is my heat pump not working?
- Check these three things before calling anyone
- The 10 causes, from harmless to serious
- Two things that look broken but are normal
- What heat pump repairs cost in Durham Region
- When to stop troubleshooting and call a pro
- Safety first
- Key terms in this article
- Frequently asked questions
Why is my heat pump not working?
A heat pump not working usually traces to one of ten causes: wrong thermostat settings, a tripped breaker, a clogged filter, a blocked outdoor unit, frozen coils, a failed capacitor, a refrigerant leak, short cycling, a stuck reversing valve, or a failing compressor. The first five are things a homeowner can check safely. The last five need a licensed technician.
Roughly a third of the "broken" heat pumps we get called about across Whitby, Oshawa, Ajax, and Pickering need no repair at all. Someone bumped a switch, a filter clogged, or the unit was doing something completely normal that looked alarming, like a winter defrost cycle. Work through the checks below in order. You will either fix the problem yourself or know exactly what to tell the technician when you call.
Heat pump not working? Check these three things before calling anyone
1. The thermostat
Confirm it is set to the right mode. A heat pump switched to heat in summer, or left in fan only, will run without ever cooling. Set the correct mode, move the target at least 3 degrees past the room temperature, and wait five minutes, since most systems have a built-in restart delay. If the screen is blank, replace the batteries. A surprising number of after-hours calls end right there.
2. The breaker and disconnect switch
Heat pumps draw from two points: a breaker in your electrical panel and a disconnect box on the wall beside the outdoor unit. Check both. A breaker that trips once can be reset. A breaker that trips again the same day is telling you something electrical is failing. Stop resetting it and call us.
3. The air filter
Pull the filter and hold it up to a light. If you cannot see light through it, the system has been suffocating. A clogged filter causes weak airflow, frozen coils, short cycling, and eventually compressor strain. Replace it, then give the system a few hours to recover. In Durham homes with pets, check the filter every 30 days rather than the 90 the packaging claims.
The 10 causes, from harmless to serious
| # | Cause | Typical symptom | Who fixes it |
|---|---|---|---|
| 1 | Wrong thermostat mode or dead batteries | Nothing runs, or the fan runs with no heating or cooling | You |
| 2 | Tripped breaker or disconnect switch off | Completely dead unit | You once; a pro if it trips again |
| 3 | Clogged air filter | Weak airflow, long run times, ice on coils | You |
| 4 | Blocked outdoor unit | Poor performance, unit runs constantly | You |
| 5 | Frozen coils | Ice buildup, little or no air movement | You to thaw; a pro to find the cause |
| 6 | Failed capacitor | Humming outdoor unit, fan not spinning | Pro |
| 7 | Refrigerant leak | Weak cooling or heating, hissing, ice | Pro, licensed only |
| 8 | Short cycling | Starts and stops every few minutes | Pro, after the filter check |
| 9 | Stuck reversing valve | Cools but will not heat, or the opposite | Pro |
| 10 | Compressor failure | Loud grinding then silence, breaker trips | Pro, often replacement territory |
Causes ranked by how often we see them on Durham Region service calls, verified August 2026.
Blocked outdoor unit (cause 4)
Walk outside and look at the condenser. Grass clippings, cottonwood fluff, leaves, and hedge overgrowth all choke the coil, and Lake Ontario winters add drifted snow and ice around the base. Clear 60 cm of open space around the unit and gently rinse the fins with a garden hose, with the power off first. Never use a pressure washer on the fins.
Frozen coils (cause 5)
Ice on the indoor or outdoor coil means the system cannot move heat. Switch the system off, set the fan to on to help it thaw, and replace the filter. Here is the part most online guides skip: the ice is a symptom, not the disease. If it freezes again after thawing, the underlying cause is usually low refrigerant or a failing sensor, and both need a technician.
Failed capacitor (cause 6)
The capacitor gives the fan and compressor motors their starting jolt. When it fails, the outdoor unit hums but the fan does not spin. This is one of the most common repairs we do and one of the cheapest, but a capacitor holds a stored electrical charge that can hurt you even with the power off. Do not open the panel yourself.
Refrigerant leak (cause 7)
A heat pump never uses up refrigerant. If levels are low, it leaked, and topping it up without fixing the leak only buys a few months. According to Environment and Climate Change Canada's ozone protection rules, handling refrigerant legally requires certification, so this is never a DIY job. Watch for gradual performance loss, a faint hissing near the lines, or ice despite a clean filter.
Stuck reversing valve (cause 9)
The reversing valve is what lets one machine both heat and cool. When it sticks, you get a heat pump that cools beautifully but will not heat, or the reverse. If your system works in one mode only, tell the technician that exact symptom on the phone. It saves diagnostic time and saves you money.
Two things that look broken but are normal
Steam and a pause in winter
On cold, damp days near Lake Ontario, frost forms on the outdoor coil and your heat pump runs a defrost cycle. The outdoor fan stops, you may hear a whoosh, and a cloud of steam rises off the unit for a few minutes. Homeowners call us about this every winter convinced something is on fire. It is the system taking care of itself. Only worry if defrost runs constantly or the coil stays iced over.
Cooler supply air than a furnace
A gas furnace blows air at 45 to 60 degrees Celsius. A heat pump in heating mode delivers 30 to 40 degrees, warmer than your skin but cooler than you may be used to, so it can feel lukewarm while heating the house perfectly well. According to Natural Resources Canada, this lower supply temperature is normal heat pump behaviour, not a fault. Check the actual room temperature against the setpoint before deciding the unit is failing.
How much does heat pump repair cost in Durham Region?
Most single-component heat pump repairs in Durham Region land between $250 and $600 CAD in 2026, with a diagnostic fee of $99 to $150 CAD that is applied toward the repair when you proceed. Refrigerant leaks and major components cost more. Every repair starts with a proper diagnosis, because guessing at parts is the most expensive way to fix a heat pump not working.
| Repair | Typical 2026 cost (CAD) | Notes |
|---|---|---|
| Diagnostic visit | $99 to $150 CAD | Applied to the repair |
| Thermostat replacement | $300 to $600 CAD | Higher for smart models |
| Capacitor replacement | $250 to $450 CAD | Most common single repair |
| Refrigerant leak repair and recharge | $800 to $2,000 CAD | Depends on leak location |
| Reversing valve replacement | $1,500 to $2,500 CAD | Labour intensive |
| Compressor replacement | $2,500 to $4,500 CAD | Compare against unit replacement |
Typical residential ranges for Durham Region, verified August 2026. Exact pricing follows an in-home diagnosis.
One honest rule of thumb we give customers: if the repair quote exceeds a third of the cost of a new system and your unit is past 10 years old, put the money toward replacement instead. A compressor swap on a 13 year old heat pump is rarely the right call, even though it is billable work for us. If replacement wins, compare current pricing in our heat pump cost guide for Durham Region, and ask about the Home Renovation Savings program for qualifying cold-climate heat pumps.
When to stop troubleshooting and call a pro
Stop and call immediately if you notice any of these: a breaker that trips more than once, grinding or screeching from the compressor, burning smells, ice that returns after thawing, or a unit that is completely dead after the thermostat and breaker checks. Each of those points to an electrical or refrigerant fault where continued running causes real damage, and a heat pump not working at that stage can turn a $300 CAD fix into a $3,000 CAD one.
Our TSSA-licensed team handles heat pump diagnosis and repair across Whitby, Oshawa, Ajax, Pickering, Courtice, Bowmanville, Port Perry, and Uxbridge, on every major brand, with 24/7 emergency service when the weather will not wait. Because our head office is at 1910 Dundas St E in Whitby, Durham calls get a local truck, not a dispatcher two regions away. If the diagnosis lands in replacement territory, we walk you through options honestly, including heat pump installation, rather than pushing a repair that does not make sense. A seasonal tune-up through our maintenance and protection plans catches most of these faults before they strand you.
Key terms in this article
- Reversing valve: the component that flips refrigerant flow so one machine can both heat and cool.
- Defrost cycle: a normal winter routine where the heat pump briefly reverses to melt frost off the outdoor coil.
- Capacitor: the part that gives the fan and compressor motors their starting jolt; it holds a charge even with power off.
- Refrigerant charge: the sealed volume of refrigerant in the system; low charge always means a leak, never normal use.
- TSSA: Ontario's Technical Standards and Safety Authority, which certifies the technicians who legally work on fuel-burning systems.
Frequently asked questions
| Your heat pump questions, answered |
|---|
| Why is my heat pump not working at all? A heat pump not working at all usually means no power or no call for operation. Check the thermostat mode and batteries, then the breaker and the outdoor disconnect switch. If the unit stays dead after those checks, a failed capacitor, board, or compressor is likely, and that needs a licensed technician. |
| Why is my heat pump running but not cooling the house? Start with the filter and the outdoor coil, since restricted airflow causes most of these calls. If both are clean, the likely culprits are low refrigerant from a leak or a failing compressor, and both need a licensed technician to confirm with gauges. |
| Why is my heat pump blowing cold air in heating mode? First rule out a defrost cycle, which reverses the system for a few minutes and is completely normal. If cold air continues beyond 10 minutes, suspect a stuck reversing valve or low refrigerant. Remember that heat pump supply air at 30 to 40 degrees feels cooler than furnace air while still heating the home. |
| Is it safe to reset a tripped breaker on my heat pump? Once, yes. If it trips again the same day, leave it off and book a repair. Repeated trips usually mean a shorting motor, a failed capacitor, or a compressor drawing excess current, and each reset risks more damage to the equipment and your wiring. |
| Why is my heat pump covered in ice? Light winter frost is normal and the defrost cycle clears it. A solid ice shell, or any ice in summer, is not. Shut the system off, let it thaw, and replace the filter. If ice returns, the cause is usually low refrigerant or a sensor fault that needs professional diagnosis. |
Do not take our word for it alone. Read our 364 verified reviews on Google, and see the Heating, Refrigeration and Air Conditioning Institute of Canada for what accredited contractors are expected to deliver.
