If your heat pump seems like it's not heating, check the air temperature at the vent before assuming anything's broken. Heat pump air in heating mode normally runs 85 to 95 degrees, well below your 98.6-degree hand, so it feels cool on skin even when the system is working exactly right.
That single fact accounts for a large share of "my heat pump isn't heating" complaints. A gas furnace pushes air near 120 degrees, which trains people to expect hot air from any heating system. A heat pump was never going to deliver that, and it doesn't need to. What matters is whether the house is actually reaching the temperature set on the thermostat, not what the air feels like against your palm.
Check the room temperature, not your hand
Before anything else, look at the thermostat. Is the room temperature climbing toward the setpoint, even slowly? If yes, the system is heating, and the cool-feeling air is a red herring. If the room temperature is flat or dropping while the thermostat calls for heat, you've got a real problem, and the rest of this guide is for you.
Thermostat set wrong
It sounds basic, but it's common. Confirm the system is set to Heat, not Cool or Auto behaving unexpectedly, and that the setpoint is actually above the current room temperature. A thermostat accidentally bumped to Auto in a house that also has a separate cooling schedule can produce confusing results. Some smart thermostats have scheduling quirks that override a manual change; check the schedule if the system seems to be second-guessing you.
Tripped breaker or disconnect
A heat pump has two power points worth checking: the breaker at the main panel and, on many installations, a separate disconnect switch near the outdoor unit. Either one being off will stop the whole system cold. If the outdoor unit is dead silent and the indoor air handler isn't running either, this is worth ruling out before anything more involved.
Dirty air filter
A clogged filter starves the system of airflow, which can trigger a safety shutoff or just tank performance to the point where the house never reaches temperature. This is the cheapest, fastest thing to check and rule out. Arizona's dust means filters here clog faster than in cleaner climates; a filter that would last three months elsewhere might need changing every four to six weeks in a dusty part of the Valley.
Outdoor unit iced over
Some frost on the outdoor coil during cold, damp weather is normal and clears on its own through the defrost cycle. A solid block of ice that isn't clearing, or ice that keeps rebuilding after each defrost attempt, is a fault, usually tied to a failed defrost control board, a bad sensor, or a fan motor that's stopped running. Our heat pump defrost cycle guide walks through what normal defrost looks like versus a failure.
Reversing valve stuck
The reversing valve is what lets the same outdoor unit switch between cooling and heating. If it's stuck in the cooling position, the thermostat can be set to Heat and calling for it correctly, but the system keeps producing cold air anyway. This is a common cause of a heat pump blowing cold air specifically when heat is expected, and it's not a DIY fix. Our heat pump blowing cold air guide covers this symptom in more depth.
Low refrigerant
A heat pump low on refrigerant, usually from a slow leak, loses capacity in both heating and cooling mode. It might still run and produce some warm air, just not enough to keep pace with the house's heat loss, especially overnight. Refrigerant work requires an EPA Section 608-certified technician; you can read the underlying rule at the EPA's Section 608 program page.
Auxiliary heat running instead of the heat pump
If the house is heating, but you notice the system seems to be leaning heavily on electric strip heat rather than the compressor, that's worth flagging separately. Auxiliary heat is supposed to be occasional backup, not the main event. A system running mostly on AUX usually means the heat pump side has a real problem underneath. Our heat pump emergency heat guide breaks down auxiliary versus emergency heat and what constant AUX usage means.
When to stop troubleshooting and call someone
Breaker, filter, and thermostat settings are safe and quick to check yourself. Ice that won't clear, a reversing valve, and refrigerant level are not. If you've ruled out the easy stuff and the house still isn't warming, that's the point to call a licensed technician rather than keep guessing. A misdiagnosed heat pump repair wastes money on the wrong part. Refrigerant or electrical work done without the right certification is a safety issue on top of that.
The Arizona context
Arizona heat pumps spend most of the year working hard in cooling mode and comparatively little time heating, since Valley winters are short and mild. That lighter duty cycle on the heating side means a lot of the failures common in colder climates, like a defrost system running constantly or a reversing valve stuck from heavy winter use, show up less often here. When a heat pump in Phoenix, Tempe, or Chandler does have a heating complaint, it's more often one of the basics: filter, breaker, or a refrigerant leak that's been slowly worsening since summer. A unit struggling on one of the rare cold nights in the Valley is not the same situation as one working overtime through a Midwest winter, and it usually points to an existing problem rather than the cold itself.
Common questions
Why does my heat pump air feel cold even though it's in heat mode?
Heat pump air in heating mode runs 85 to 95 degrees, cooler than your 98.6-degree hand and far cooler than the roughly 120-degree air a gas furnace produces. It will feel cool by comparison even while heating correctly. Check the room temperature against the thermostat setpoint instead of judging by touch.
What's the first thing to check if a heat pump won't heat at all?
Confirm the thermostat is set to Heat with a setpoint above room temperature, then check the breaker and any disconnect switch near the outdoor unit. Those three take a few minutes and rule out the most common non-mechanical causes before you assume a part has failed.
Can a dirty filter really stop a heat pump from heating?
Yes. A clogged filter restricts airflow enough to trigger a safety shutoff on some systems or simply tank heating capacity so the house never reaches the setpoint. It's the cheapest thing to check first, and Arizona dust means filters here need changing more often than in cleaner climates.
Is a heat pump not heating a bigger deal in Arizona winters?
Less often than in colder states, since Arizona winters are short and mild and heat pumps here see light duty on the heating side. When a heating complaint does show up, it's usually a basic issue like a filter, breaker, or a refrigerant leak rather than the kind of defrost or reversing valve strain seen in colder climates.
Should I try emergency heat if my heat pump won't heat?
Only if you already know the heat pump itself has failed, such as a confirmed frozen outdoor unit or dead compressor. Emergency heat runs the house on electric strips alone and costs more to operate. Flipping to it before diagnosing the actual problem just adds to the power bill without fixing anything.
Get it diagnosed properly
Cheap checks first: thermostat, breaker, filter. If the house still isn't heating after that, get a technician out rather than guessing at parts. Use the quote form below to get matched with licensed heat pump contractors in Scottsdale and Tempe, or see our heat pump repair guide for what these fixes typically cost.