Heat Pump Not Working? 7 Fast Fixes Before You Panic

If your heat pump not working has left your home too hot, too cold, or eerily silent, you’re not alone — and most causes are easier to diagnose than homeowners expect. This guide covers what to do whether your heat pump stopped working overnight, won’t start after a power blip, or has simply gone quiet mid-cycle.

By the end, you’ll know exactly what to check yourself, what points to a real emergency, and when it’s time to call a licensed technician. No fluff — just a clear diagnostic path you can apply to your own system today, whether you’re searching “why is my heat pump not working” or troubleshooting a specific symptom.

Unlike a furnace or a standalone air conditioner, a heat pump runs in two directions all year, moving heat into your home during winter and pulling it out during summer. That means a heat pump that stopped working can point to very different problems depending on the season — exactly why this guide is broken into mode-specific sections below.

Step One: A Quick Safety Check

Before touching anything, take thirty seconds for a safety check. Turn off the system at the thermostat if you smell burning, see sparks, hear buzzing from the electrical panel, or notice the outdoor unit’s fan is jammed but still trying to spin. These are signs of an electrical fault, not a simple maintenance issue, and continuing to run the unit can damage the compressor or create a fire risk.

• Smell of burning plastic or wiring — shut off power at the breaker immediately
• Visible ice covering more than the coil (ice on the cabinet or refrigerant lines)
• Water pooling near the indoor air handler
• A breaker that trips repeatedly when you reset it

If none of these apply, it’s safe to work through the troubleshooting steps below.

The Heat Pump Won’t Turn On, Won’t Start, or Isn’t Running

Whether you’d describe it as the heat pump won’t start, isn’t running, or is completely dead, this is the most common complaint we hear — and it’s usually one of four things.

Check the Thermostat First

Confirm the thermostat is set to heat or cool as needed, the temperature is actually set past the current room temperature, and the display has power. A dead thermostat battery looks identical to a dead heat pump from the homeowner’s chair.

Check the Breaker and Disconnect Switch

Heat pumps typically have two power points: the breaker in your electrical panel and a disconnect switch (often a grey box) mounted beside the outdoor unit. Both need to be in the “on” position. A tripped breaker that resets and trips again within minutes usually means an electrical short and needs a technician, not a repeated reset.

Check for a Blown Fuse in the Outdoor Disconnect

Some disconnect boxes contain pull-out fuses. If the unit hums but doesn’t start, or is completely silent, a blown fuse is a common and inexpensive culprit.

Want a faster, guided way to narrow this down? Our heat pump troubleshooting wizard below walks through these checks interactively based on your symptoms.

The Heat Pump Runs but Produces No Heat or No Cooling

This is a different problem from a heat pump that won't start, and it points to airflow or refrigerant issues rather than electrical ones.

Dirty or Clogged Air Filter

A clogged filter restricts airflow across the indoor coil, which can cause weak heating, weak cooling, or the coil freezing entirely. Check the filter monthly during peak season and replace it if you can't see light through it. Filter changes are also the single most effective habit covered in our heat pump maintenance guide.

Blocked Outdoor Unit

Leaves, snow, ice buildup, or anything piled against the outdoor unit restricts the airflow the system needs to exchange heat. Keep at least 60 cm (about two feet) clear on all sides, and after a snowfall, clear the top and sides so the fan isn't obstructed.

Low Refrigerant Charge

If the system runs constantly but never reaches the set temperature, and you notice the outdoor coil frosting even in mild weather, low refrigerant is a likely cause. This isn't a DIY fix — refrigerant handling in Canada is regulated, and a licensed technician needs to locate the leak, repair it, and recharge the system properly.

Reversing Valve Stuck

The reversing valve is what allows a heat pump to switch between heating and cooling. If your system blows cold air when set to heat, or warm air when set to cool, a stuck reversing valve is often the reason. This requires a professional diagnosis, and it's one of the reasons heat pump lifespan can vary so much — see our heat pump lifespan guide for what to expect as components age.

For a clearer picture of what proper heating output should cost to run, the heat pump operating cost calculator below can help you spot whether your system is drawing more power than it should for the heat it's producing.

Heat Pump Frozen or Covered in Ice

A light, even layer of frost on the outdoor coil during a defrost cycle in winter is normal. A heat pump that stays frozen or builds up thick ice is not. Understanding how the defrost cycle is supposed to work makes it much easier to spot when something has actually failed.

Common causes include a blocked filter or coil restricting airflow, low refrigerant, a failed defrost control board, or a fan motor that has stopped spinning. Don't chip at the ice, since this can damage the coil fins. Instead, turn the system off, let it thaw naturally or with a gentle fan, and call for service if the ice returns within a day or two of restarting.

Strange Noises or Smells Coming From the Unit

Sounds tell you a lot about what's failing inside a heat pump.

• Clicking on start or stop: usually normal relay operation
• Buzzing: often an electrical or contactor issue, worth a technician visit
• Grinding or squealing: typically a failing fan motor bearing
• Banging: can indicate a loose or broken internal component, particularly the compressor
• Burning smell: shut the system off and call a technician right away
• Musty smell: often mould or moisture in the ductwork or drain pan, not usually an emergency but worth addressing

Quick Symptom Reference Table

Use this table to jump straight to the likely cause and whether it's safe to handle yourself.

Symptom	Likely Cause	DIY or Technician
No power at all	Tripped breaker, blown fuse, dead thermostat battery	DIY first
Runs, but no heat	Dirty filter, blocked outdoor unit, low refrigerant	DIY check, then technician
Blows cold air in heat mode	Stuck reversing valve	Technician
Coil frozen or iced over	Airflow restriction, low refrigerant, failed defrost board	Technician
Buzzing or grinding noise	Failing contactor or fan motor bearing	Technician
Breaker trips repeatedly	Electrical short or failing compressor	Technician (urgent)

Heat Pump Not Working After a Snowstorm, Power Outage, or Extreme Cold

Ontario homeowners from Toronto and Ottawa to Hamilton, London, Kingston, and Sudbury deal with a specific version of this problem every winter: a heat pump that was working fine before a cold snap, freezing rain, or a hydro outage, and stops cooperating right after.

A few weather-specific patterns are worth knowing:

• After a power outage: the system may need a manual reset at the breaker, and the thermostat's schedule or settings can reset too — check both before assuming a fault
• After heavy snow accumulation: snow packed around or on top of the outdoor unit blocks airflow and can trigger the same symptoms as a dirty filter — dig it out and give it space
• During extreme cold below -20°C: most cold-climate heat pumps are rated to keep working, but output naturally drops, and homes without a backup heat source may feel the difference more — this isn't necessarily a malfunction
• After freezing rain: ice can coat the outdoor unit's housing and fan blades even before the coil itself freezes — a visual check is worth doing before troubleshooting further

If cold-weather performance has been a recurring issue rather than a one-off, it may be worth reviewing whether your current unit is properly sized and rated for Ontario winters in our heat pump buying guide.

DIY Troubleshooting Checklist Before You Call for Service

Run through this list first. It solves a surprising share of "heat pump not working" calls without needing a technician visit.

1. Confirm the thermostat is set correctly and has working batteries
2. Check both the breaker and the outdoor disconnect switch
3. Replace the air filter if it looks dirty
4. Clear debris, snow, or ice from around the outdoor unit
5. Look for ice buildup on the coil
6. Listen for unusual noises and note when they happen
7. Check that all supply and return vents inside the home are open and unblocked

If you've gone through this checklist and the system still isn't performing, the heat pump recommendation wizard below can help you understand whether a repair or a replacement makes more financial sense based on your system's age.

Is This a True Emergency or Can It Wait?

Not every heat pump problem needs a same-day call. Here's how to tell the difference.

Call for Emergency Service If:

• You smell burning or see smoke or sparks
• The breaker trips repeatedly no matter how many times you reset it
• There's standing water near the indoor unit
• Outdoor temperatures are dangerously low or high and you have no backup heating or cooling source

It Can Likely Wait for a Scheduled Visit If:

• The system runs but is slightly less efficient than usual
• You hear a minor noise that isn't getting worse
• The home is holding a comfortable temperature even if the system is working harder than normal

What Repairs Typically Cost

Costs vary by region and the age of your equipment, but this table gives a general sense of what to expect in Ontario (CAD). Always get a written quote before authorizing work.

Issue	Typical Cost (CAD)
Capacitor or contactor replacement	$150 – $400
Refrigerant leak repair and recharge	$400 – $1,800
Fan motor replacement	$350 – $900
Defrost control board replacement	$250 – $600
Reversing valve replacement	$500 – $1,200
Compressor replacement	$1,800 – $3,500

Ranges reflect typical Ontario installer quotes as of 2026 and vary by brand, capacity, and home. Always confirm with a local estimate.

If a repair estimate is climbing close to the cost of a compressor, it's worth comparing against replacement. Use the heat pump cost calculator below to see what a new install would run.

For the long-term picture, our heat pump savings calculator and is a heat pump worth it quiz can help you sanity-check the decision if your current unit is older than ten years. For homeowners weighing sizing during a replacement, the heat pump size BTU calculator gives a starting estimate before a technician does a full load calculation. Our heat pump brands comparison and installation guide are also worth a look if repair costs are pushing you toward a new system.

Seasonal Heat Pump Maintenance Calendar

A lot of "heat pump not working" calls are preventable with a simple year-round routine. Here's what to check each season.

Season	What to Check
Spring	Book an annual tune-up, clear winter debris from the outdoor unit, test cooling mode before hot weather arrives
Summer	Replace or clean the filter monthly, keep the outdoor unit free of grass clippings and leaves
Fall	Confirm the reversing valve switches cleanly to heat mode, check for unusual noises before peak heating season
Winter	Clear snow and ice from the outdoor unit after every storm, monitor for excessive frost buildup, avoid blocking indoor vents

For the full year-round routine, see our complete heat pump maintenance guide.

Related Cooling Tools

Since many heat pumps also handle summer cooling, these calculators are useful if your symptoms show up more in cooling mode than heating mode:

• AC troubleshooting wizard for cooling-specific symptoms
• AC repair cost calculator for a quick repair estimate
• AC size & tonnage calculator for sizing questions
• AC cost calculator to compare unit pricing
• AC operating cost calculator to check running costs
• AC savings calculator for efficiency upgrades
• AC recommendation wizard for repair versus replace guidance

For more background on how heat pumps compare to furnaces before you decide on a repair versus a full switch, see our heat pump buying guide and our roundup of the best heat pumps in Canada. According to Natural Resources Canada, properly maintained heat pumps remain one of the most efficient heating and cooling options for Canadian homes. The ENERGY STAR program is also a reliable reference point when comparing efficiency ratings on a replacement unit.

Final Thoughts

Most cases of a heat pump not working come down to a handful of repeatable causes: power issues, airflow blockages, refrigerant problems, or a failing component like the reversing valve or defrost board. Working through the checklist above will solve many of these on your own, and for anything involving refrigerant, electrical faults, or repeated breaker trips, a licensed technician should take over.

If your system is still not cooperating after troubleshooting, reach out for a free quote and a technician can get your comfort back on track quickly.

Frequently Asked Questions