First — what kind of heat do you have?

• Heat pump — the most common in South Florida. Same outdoor unit as your AC; runs in reverse for heating.
• Heat pump + electric strip backup — a heat pump with electric resistance heating built into the air handler for cold snaps below 35°F outside.
• Gas furnace — uncommon in PB/Broward; more common in older homes north of Stuart.
• Electric strip only — older condos and apartments. Big electric bills, slow heat-up.

The diagnosis flow depends on which you have. Check your air handler — if there’s a gas line, you have a furnace; if not, it’s a heat pump or strip-only system.

Heat pump diagnosis

1. Thermostat set to HEAT and at least 3°F above current room temp? (Heat pumps won’t kick on for tiny gaps.)
2. Outdoor unit running? Walk outside. The fan should spin when the system calls for heat. If it’s silent and you can hear the indoor blower, the heat pump is dead — the strips alone are heating you (slowly, expensively).
3. Frost on the outdoor unit? Normal in cold weather. The unit goes through “defrost cycles” automatically. If outdoor unit is iced over and not defrosting, the defrost board has failed — needs a tech.
4. Air feels lukewarm but not warm? This is normal for heat pumps — supply air runs 90–95°F vs 130°F+ for furnaces. It feels less warm but it heats the room just fine over time.

Cold air blowing — the #1 panic call we get

If your heat pump is in defrost cycle, the indoor blower may temporarily blow cold air for 5–8 minutes while the outdoor unit melts ice off itself. This is normal and expected. Don’t turn the system off — wait it out.

If cold air is blowing for more than 15 minutes, then check:

• Reversing valve stuck — system thinks it’s in cooling mode. Tech repair, $400–$650.
• Refrigerant leak — won’t make heat properly. Tech.
• Outdoor sensor failed — system can’t tell if it’s cold and stays in cool. Tech, $200–$300.

Electric strip backup not engaging

On nights below 35°F outdoor, your strips should kick in automatically when the heat pump can’t keep up. Symptoms of failed strips:

• Indoor temp slowly drops below setpoint, can’t recover.
• “AUX HEAT” or “EM HEAT” indicator never lights on thermostat.
• Tripped breaker — strips draw 40–60 amps; old breakers fail under load.

Most homes have 2 strip breakers; check both.

Gas furnace won’t ignite

1. Gas valve open? Look at the line near the furnace — perpendicular to the pipe = closed; parallel = open.
2. Flame sensor dirty? The most common furnace issue. Sensor sees no flame, shuts gas off. DIY clean: turn off power, remove the rod-shaped sensor, lightly sand it with fine sandpaper, reinstall. Or have a tech do it ($150).
3. Pilot/ignitor failed? If you hear clicking but no ignition, the hot-surface ignitor or spark electrode is bad. $250–$350 repair.
4. Pressure switch — if the inducer fan runs but ignition doesn’t happen, the pressure switch may be bad or vent is blocked. Don’t override it; needs a tech.

FAQ

Why is my heat bill 3× normal in January?
You’re likely running on electric strip backup because the heat pump failed. A heat pump uses about $1.20 of electricity per dollar of heat output; strips use exactly $1 of electricity per dollar of heat. So strips cost ~3× more per BTU.

Is “EM HEAT” the same as regular heat?
No. EM HEAT bypasses the heat pump entirely and runs only on electric strips. Use it only when the heat pump is broken — it’s expensive. Switch back to regular HEAT as soon as repairs are done.

How often should I service heat?
Annual pre-winter check. Our Comfort Plan includes a heating tune-up in October–November so you’re not the one calling at 11pm during the first cold front.

Need it diagnosed today?

AtlantFlow runs same-day service across Palm Beach, Broward, and Miami-Dade. Licensed FL CAC1824422.

Call (561) 510-9414