Heat Pump Not Heating in Tempe? What's Wrong and What It Costs (2026)
Heat pump on, house still cold? What you see at the thermostat and the outdoor unit tells you which part failed. The Tempe causes, three free checks, and repair prices.
Most Tempe homes heat with a heat pump, and most of them sit in cooling mode from March to November. So the first cold morning is the first time in eight months the heat side has been asked to do anything. That's when we get the call: "it's running, but the house won't warm up."
Arizona heat pumps don't fail because it's too cold. A working heat pump handles a 38° Tempe morning without trouble. If yours can't, something broke. What you see at the thermostat and at the outdoor unit tells you what.
First: what is it doing?
- Blowing air, but the air is cold. Reversing valve, defrost board, or refrigerant. Could also be a normal defrost cycle if it lasts only a few minutes. Our cold-air guide covers how to tell.
- Blowing lukewarm air, house never reaches the setpoint. Low refrigerant, a dirty or bent outdoor coil, or a system that's too small for the house.
- Thermostat shows Aux Heat all the time. The heat pump can't keep up and the electric strips are carrying the house. It'll show on the SRP bill within weeks.
- Outdoor unit iced over. The defrost cycle isn't running. Defrost sensor, defrost board, or outdoor fan motor.
- Nothing at all. No air, no sound. Thermostat, breaker, or a control problem. Start with the checks below.
Three checks before you call
- Thermostat. Mode on HEAT (not COOL or AUTO), setpoint a few degrees above room temperature, fan on AUTO. If the screen is blank, change the batteries; blank thermostat guide here.
- Breakers. A heat pump has two: one for the outdoor unit and one for the air handler and heat strips. Check both, and the disconnect box by the outdoor unit. Reset once. If it trips again, stop; here's why.
- Filter. A clogged filter cuts airflow, and low airflow cuts heat output fast. If you can't remember changing it, change it.
If the house still isn't warming up in 30 minutes, set the thermostat to OFF and call. Running a heat pump with a failed part is how a $495 repair turns into a compressor.
The usual causes in Tempe
Reversing valve stuck in cooling. The valve that switches the unit from cooling to heating has sat in one position since spring. If the solenoid coil burned out, it's a small repair. If the valve itself is stuck, it's sealed-system work.
Defrost board or sensor. In heat mode the outdoor coil gets cold enough to frost over. The board runs a short defrost cycle to clear it. When the board or sensor fails, the coil ices solid and heat output drops to almost nothing.
Low refrigerant. Heating asks more of the refrigerant charge than cooling does, so a slow leak that barely showed up in August shows up in the first cold week. Low means it's leaking. We find the leak; we don't top it off.
Heat strips or sequencer. The strips cover defrost cycles and the coldest mornings. When they're dead, defrost feels freezing and the house drops a few degrees before sunrise.
Capacitor or outdoor fan motor. Same parts that fail in July. No outdoor fan, no heat exchange, and the unit shuts itself off or ices up.
Bent or dirty outdoor coil. Hail and summer dust both cut how much heat the coil can pull from outside air. Bent fins explained.
What the repairs cost
Installed, parts and labor, our Tempe prices. Full table on the heat pump repair page.
| Diagnostic visit | $59.95 | Waived when you approve the repair |
| Capacitor | $165–$245 | Most common failure, any season |
| Defrost board or sensor | $495 | The "iced over" fix |
| Heat strip or sequencer | $495 | Per element |
| Thermostat | $295 | Heat pumps need the O/B setting right |
| Refrigerant leak repair + recharge | $500–$1,500 | Leak found and fixed, not topped off |
| Reversing valve | $1,695 | Repair-or-replace on anything past 12 years |
On a system past 12 years, a reversing valve or compressor gets both numbers on the same sheet: the repair and the replacement. Our repair-or-replace guide has the math.
Aux heat and emergency heat
Aux heat turns on by itself when the heat pump needs help: during defrost, on the coldest mornings, or when you raise the setpoint several degrees at once. A few minutes is normal. All day is a repair.
Emergency heat is a switch you flip. It shuts the heat pump off and runs only the strips. Use it if the outdoor unit is iced solid, not running, or damaged, and only until the repair. It costs three to four times as much per hour as the heat pump does.
Why now
A Tempe heat pump ran thousands of hours this summer. The capacitor and fan motor are worn, the defrost board hasn't cycled since February, and the reversing valve hasn't moved since spring. A fall tune-up runs the system in heat mode, forces a defrost, and tests every heat strip before the cold morning does. $59.95 per system, same tune-up we run in spring.
Questions people ask
Why is my heat pump running but not heating the house?+
In Tempe the common causes are a reversing valve stuck in cooling, a failed defrost board, low refrigerant from a leak, or dead heat strips. Check the thermostat is on HEAT, both breakers are on, and the filter is clean first. If it still won't warm up in 30 minutes, turn it off and call.
Is it normal for a heat pump to struggle in Arizona winter?+
No. A working heat pump handles Tempe's coldest mornings easily. If it can't keep up at 35 to 45 degrees, a part has failed, the system is low on refrigerant, or it was undersized.
Why does my thermostat say Aux Heat all the time?+
The heat pump can't keep up and the electric heat strips are doing the work. Strips cost three to four times more to run, so it shows up on the SRP or APS bill fast. It usually means low refrigerant, a defrost problem, or a failing part.
How much does it cost to fix a heat pump that isn't heating?+
In Tempe most repairs run $165 to $500: a capacitor $165 to $245, a defrost board or heat strip $495. A refrigerant leak repair is $500 to $1,500, and a reversing valve is $1,695. Our $59.95 diagnostic is waived when you approve the repair.
Should I use emergency heat?+
Only if the outdoor unit is broken: iced solid, not running, or hail-damaged. Emergency heat shuts the heat pump off and runs only the electric strips, which is expensive. Use it until the repair, then switch back.