If your heat pump is blowing cool air, start with the thermostat mode, the filter and the outdoor unit. Normal lows at the airport sit around 40F in December and January, and on the colder mornings some of what looks like a failure is the defrost cycle. Climate Pros Tucson can match you with a licensed pro if the checks below don’t fix it.
How cold does Tucson get?
The City of Tucson’s winter design temperature is 35F, and the airport averages fewer than 12 nights a year at or below 32F. Most mornings are mild for heat pump duty. A heat pump that can’t heat the house on a normal Tucson morning has a problem.
What should you check first?
- Thermostat mode. It must say Heat, not Cool, and the setpoint must sit above the room temperature.
- Filter. A clogged filter chokes airflow and makes the air feel cool.
- Breaker. Check the breakers for both the indoor and outdoor units.
- Outdoor unit. Look for leaves, sticks or a blocked fan. Keep clear space around it.
- Batteries in the thermostat. Dead batteries cause odd behavior.
Is the steam or frost normal?
Yes, in short bursts. In heating mode the outdoor coil gets cold and can frost. The unit then briefly reverses to melt the frost, called a defrost cycle. You may see steam and hear a whoosh, and the indoor air can feel cooler for a few minutes. That’s normal. A coil that stays iced for a long stretch isn’t. See frozen or steaming heat pump outdoor unit.
What’s emergency heat?
Many thermostats have an Emergency or Aux setting. It switches to electric resistance heat and bypasses the heat pump. Use it only to bridge a breakdown. It uses much more electricity, and TEP’s winter on-peak windows are 6 to 9 a.m. and 6 to 9 p.m., Monday to Friday, so a morning on emergency heat can land in the priciest window. If you need emergency heat for more than a short stretch, call a pro.
What are the signs of a real fault?
- Air stays cool for more than a short defrost.
- The outdoor unit doesn’t run at all.
- The unit short cycles.
- A stuck reversing valve keeps the system in cooling mode. Read about the heat pump reversing valve.
- Ice buildup that doesn’t clear.
- Strange noises or a burning smell. Shut it off.
What about higher elevation?
On Mount Lemmon, Summerhaven sees about 53 freezing nights a year at a nearby station, and heating needs run roughly three times the airport’s. A heat pump there may need backup heat, and that’s a decision for the pro.
Can a heat pump heat enough in Tucson?
Usually, yes. See do heat pumps work in Tucson winters and heat pump maintenance. Read about heat pump service too, and our Tucson hub.
When to call us
If the basics don’t fix it, a licensed pro should test the system. Don’t run emergency heat for long. Call (520) 353-2520 and we’ll match you with a licensed local pro.