Check the thermostat mode first, then both breakers, then the filter. That sequence resolves a surprising number of the calls we get on the first cold night of the year, and it takes about four minutes. What it does not resolve is a real fault, and this article is mostly about telling one from the other before you spend a night guessing.
Florida winters are short. The cold snaps inside them are real, they arrive within a day or two of a forecast, and they land on equipment that has not been asked to produce heat since roughly February.
Heating here works nothing like heating up north
Most Tampa Bay homes have no furnace. What you have is a heat pump, which is the same outdoor unit that cooled you through August running its refrigerant cycle backwards, pulling heat out of cold outdoor air and delivering it inside. Backing that up is a bank of electric resistance elements in the air handler, usually called strip heat or auxiliary heat, which switch on when the heat pump alone cannot keep up.
That matters because almost every heating troubleshooting article on the internet was written for a gas furnace in a cold climate. Pilot lights, igniters, flame sensors, gas valves: none of it exists in your house. Advice about bleeding a boiler, checking a flue, or listening for the click of an igniter is worse than useless when the heat you are missing comes from a condenser sitting beside the driveway, and following it wastes the hours you should have spent on the four things that actually apply.
It has a second implication that catches people out. A heat pump failure in January is frequently the same fault that would have stopped it cooling in July. A bad capacitor, a failed contactor, a low refrigerant charge, a seized fan motor: all of those take out heating and cooling together, because it is one machine doing both jobs. You simply happened to find it in the cold.
The four checks worth doing yourself
Work through these before you call anyone. Each one is safe, and each one accounts for a meaningful share of no-heat calls.
- Thermostat mode and setpoint. Set it to Heat, not Auto, and push the setpoint at least three degrees above the current room temperature so the system has a clear reason to start. While you are there, replace the batteries. Dead batteries in a battery-powered thermostat produce a completely dead system, and it is the single most common cause we find on a first cold night.
- Every breaker, not only the obvious one. A heat pump normally has two circuits, one for the outdoor unit and one for the air handler, and the strip heat frequently has its own additional breaker or a pair of them. A tripped breaker does not always look tripped, so switch each one fully off and back on.
- The filter. Pull it and hold it up to a light. A filter you cannot see light through restricts airflow enough to trip the system on a high-limit safety, which produces exactly the symptom you are chasing.
- Registers and returns. Furniture pushed against a return grille over the summer, or closed vents in unused rooms, starve the system the same way a dirty filter does.
If the outdoor unit is running, the indoor blower is running, and the registers are blowing cool air instead of warm, stop. That is a fault, not a setting.
Frost on the outdoor unit is usually the system working
Heat pumps ice up. Pulling heat out of cold damp air chills the outdoor coil below freezing, moisture in the air condenses on it and turns to frost, and the system periodically runs a defrost cycle to melt it off. During defrost you will hear the outdoor fan stop, then a solid whoosh as the reversing valve shifts, and you may see steam rising off the unit like something is badly wrong. Nothing is wrong. Ten or fifteen minutes later it goes back to heating.
What is not normal is a unit buried in ice that never clears through several hours, or one that runs defrost constantly and never settles into a heating cycle. Either points at a failed defrost control, a bad sensor, or low refrigerant charge, and all three need a technician with gauges.
Do not chip at the ice. The aluminum fins bend under almost no force and the copper tubing behind them punctures easily, which turns a control board repair into a coil replacement.
What the emergency heat setting really does
Emergency heat, sometimes labeled Em Heat or Aux, shuts the heat pump out of the picture entirely and heats the house with the electric resistance strips alone. It works. It also converts electricity to heat at roughly one to one, while the heat pump you just bypassed moves several units of heat for every unit of electricity it consumes, so your cost per hour climbs sharply.
Use it to get through a night when the outdoor unit has quit. Do not use it as a season-long workaround.
Running on emergency heat for more than a day or two is a signal that something needs fixing, and the bill that arrives a month later tends to make the point more forcefully than we can.
What the technician does when they arrive
Knowing the shape of the visit makes it easier to judge whether you are being told the truth. A no-heat call on a heat pump starts at the thermostat, confirming it is calling for heat and that the call is reaching the equipment, then moves to the air handler to check voltage at the board, the condition of the strip heat elements and their sequencers, and the limit switches that shut everything down when airflow is poor. Outside, the technician checks the contactor, the capacitor, the reversing valve and the defrost board, and takes refrigerant pressures with the system running in heating rather than cooling.
Most failures on the first cold night land in a short list: a failed capacitor, a stuck or burnt contactor, a reversing valve that will not shift, a defrost board that has quit, a tripped high-limit from a filter nobody changed, or one bank of strip heat that opened up. Whatever it turns out to be, the cost is quoted to you before the work starts.
None of this takes long when the diagnosis is clean.
The waiting is more dangerous than the outage
More harm comes from how people heat a house during a failure than from the failure itself. Portable electric heaters need three feet of clear space around them in every direction, they belong plugged directly into a wall outlet, never an extension cord or a power strip, and they should be switched off when everyone goes to bed. Never heat a room with a gas range, an oven, a charcoal grill or a generator brought indoors or into a garage. That is carbon monoxide, it is odorless, and it kills people in this state every winter.
Close off rooms you are not using, open curtains on the sunny side during the day and shut them at dusk, and put blankets where the people are.
If the house has an infant, an elderly resident, or anyone with a medical condition affected by cold, and the indoor temperature is dropping, treat it as urgent. Our emergency service runs across the whole Tampa Bay area, and because a Florida cold snap lasts days, not months, one same-day repair generally carries you through the whole event. Before next winter, book an autumn maintenance visit. That is where most first-cold-night failures get caught, months early and on a weekday, and our seasonal guidance covers the rest.
