A heat pump that runs but doesn't seem to heat is one of the most confusing HVAC problems — partly because some of what feels wrong is actually normal. Let's separate the two, then walk through the real causes.
First, what's normal: heat pump air feels cooler than furnace air. A furnace blows air around 120–140°F; a heat pump delivers roughly 85–95°F — warmer than your body temperature but cool against your hand. Heat pumps also run in long, steady cycles rather than short blasts, and they periodically go into defrost mode (steam off the outdoor unit, a whoosh of cool air indoors for a few minutes). None of that means it's broken.
Now the real problems. Restricted airflow tops the list — a clogged filter, closed vents, or a dirty indoor coil starves the system. Check and change your filter first; it's free and it fixes more heating complaints than anything else.
Low refrigerant is the next most common cause. Because the system moves heat using refrigerant, even a modest leak means noticeably weaker heating, longer run times, and rising bills. This needs a licensed technician to find and repair — not a top-off.
Outdoor unit problems: a heat pump can't pull heat from air it can't move. Ice buildup that doesn't clear during defrost, leaves or debris packed against the coil, or a fan that isn't spinning will all cripple heating output. Clear anything blocking the unit — and if it's encased in ice, that's a defrost failure worth a service call.
Also worth checking: a thermostat set to EM HEAT (running expensive strips instead of the efficient heat pump), a failing reversing valve — the part that switches the system between heating and cooling — and, in genuinely cold weather, simply reaching the system's balance point where auxiliary heat should be kicking in automatically.
One honest note for Carolina homeowners: if your heat pump is undersized or aging, it may struggle only on the coldest mornings and be fine the rest of the winter. That's a comfort decision, not necessarily a breakdown — and worth discussing before you replace anything.
If a fresh filter and a clear outdoor unit don't fix it, let us take a look. Reinhardt Heating and Air services all makes and models across Lincoln, Gaston, Mecklenburg, and Catawba counties, 7am to midnight.