Heat Pump Not Heating? What to Check Before You Call
Cold air from your heat pump is not always a breakdown, so here are the safe checks to run, what aux heat and the defrost cycle really mean, and when it is time to call.
Start with the thermostat, breaker, and filter
Make sure the thermostat is set to Heat, not Cool or Off, and that the target is a few degrees above the room temperature. If the screen is blank or dim, swap the batteries. Check that the breakers for the indoor unit and the outdoor unit are on, then look at your air filter. A clogged filter chokes airflow, and a heat pump with weak airflow feels like it is barely trying.
Check the outdoor unit, hands off
Walk out and look at the outdoor unit. Leaves, snow, or debris packed against the sides block airflow, and you can clear loose material by hand after switching the thermostat to Off. Some frost on the coil in cold weather is normal, but do not chip, pry, or poke at ice, and never take panels off because the fins bend easily and the unit has live electrical parts.
The defrost cycle: when cool air is normal
On a cold, damp Northern Virginia morning, frost builds on the outdoor coil, so the heat pump runs in reverse for a few minutes to melt it. During that time the outdoor fan stops, steam may rise off the unit, and the air from your vents can feel cool. A normal defrost cycle usually lasts about 5 to 15 minutes and repeats now and then. If the cool air lasts much longer, or the unit stays iced over between cycles, the defrost system may not be doing its job.
Aux heat and emergency heat, in plain language
Aux heat is the backup heat inside your system, either electric heat strips in the indoor unit or a furnace in a dual fuel setup. It kicks in on its own during a hard cold snap, during defrost, or when the heat pump falls behind, and that is normal. Emergency heat is different. It is a setting you choose on the thermostat that locks out the heat pump and runs the backup alone, which costs more to run and only makes sense as a short-term bridge. If AUX stays lit on a mild day and the house still will not warm up, the heat pump itself needs a look.
When to stop checking and call
Call if the outdoor unit stays coated in ice for hours, a breaker trips again after one reset, or the air stays cold well past a normal defrost cycle. If you smell burning or see smoke, shut the system off at the breaker and call 911 if there is any fire. If you want a pro to look, call VIP General HVAC Services at (571) 761-5379. We are licensed and insured in Virginia and work across Loudoun and Fairfax County from Ashburn.
Common questions
Is it normal for my heat pump to blow cool air in winter?
Yes, for short stretches. During a defrost cycle, cool air from the vents is normal for a few minutes. Heat pump air also runs warmer than the room but cooler than a gas furnace, so it can feel lukewarm even when everything works. If the air stays cold for more than 15 minutes or the house keeps losing temperature, call for a check.
Should I switch to emergency heat if my heat pump is not heating?
Only as a short-term bridge. Emergency heat runs the backup alone, which costs more to run, and it does not fix whatever stopped the heat pump. If you find yourself relying on it, get the system looked at.
Can I chip the ice off my outdoor unit?
No. The fins and tubing damage easily, and a screwdriver or hammer can turn a defrost problem into a refrigerant leak. Clear loose snow and leaves by hand, let the defrost cycle work, and call if the ice stays put.
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