Heat pumps in Tucson spend most of the year cooling. The first cold mornings are when owners see the outdoor unit do something they have never watched. Defrost is supposed to happen. The system briefly reverses, melts frost off the outdoor coil, and may send cooler air indoors for a few minutes while strips, if the thermostat allows them, take the edge off. A white cloud that fades, with no burning smell, can be that cycle. It is water turning to vapor. It is not proof the compressor died overnight.
Smoke is the other cloud. It smells sharp or like burning insulation, it may keep coming after you set the thermostat to Off, and it is a reason to leave the equipment off and, if you smell gas or an alarm sounds, to leave the house. That path is heater smells and carbon monoxide safety, not a defrost article. Do not stand over the unit to decide. If you cannot tell steam from smoke, shut the system off and describe what you saw.
Emergency Heat is the wrong button for a cloud that faded. On a lot of thermostats that mode locks out the compressor and runs resistance strips only. Strips are expensive to run and they are a backup. The page that walks through the word on the display is Emergency Heat. Cool air at the vents for a few minutes, then heat again, is also covered on heat pump blowing cold air. If the air stays cold, the thermostat never returns to Heat, or the outdoor unit ices into a solid block and stays there, the repair conversation is heat pump repair.
Tucson nights do not always freeze. A midtown house can go most of a winter without frost on the roof, while a clear morning in Oro Valley or along the foothills drops enough for a light frost. Defrost can still run on a damp, cool coil that never reached a hard freeze. Do not wait for a weather record before you believe the cloud was real, and do not assume every cloud is a failure because the airport temperature was above freezing. The first time you test heat each fall is the first cold night, ideally before you need it.
We do not adjust defrost boards or sensors. Sabino Creek refers the request to an independent contractor if you ask us to. The license, the diagnosis, and the price are theirs. Confirm the license at roc.az.gov.
On the form choose No heat. Say whether the cloud cleared, what the thermostat displayed, and whether the indoor air recovered. ZIP required. Higher-elevation neighborhoods can add the area name. You are requesting a follow-up, not reporting that we will be in the yard at dawn.