Heat pump not heating?

What usually causes this

These are the common possibilities, not a diagnosis. A page cannot tell which one it is — that takes a technician testing the system.

Thermostat setup

Wrong mode, or a thermostat that isn't configured for a heat pump, can stop it heating properly or send it to backup heat at the wrong times.

Restricted airflow

A dirty filter or blocked returns reduce heating capacity just as they reduce cooling.

Outdoor coil iced over

Light frost is normal and melts during defrost. A solid block of ice means defrost isn't working.

Low refrigerant charge

A leak hurts heating as much as cooling, and sometimes more.

Reversing valve

The valve that switches the system between heating and cooling can stick, leaving the system blowing cool air.

Very cold weather

A heat pump's capacity falls as outdoor temperature drops. On the coldest nights, backup heat is designed to help.

What you can safely check yourself

• Set the thermostat to Heat (not Emergency Heat) and the fan to Auto.
• Replace a dirty filter and open all returns.
• Look at the outdoor unit. Light frost and steam during defrost are normal; a thick block of ice is not.
• Clear snow, leaves or debris from around the outdoor unit.

What we check when we get there

1. 1The technician checks the thermostat configuration, airflow, refrigerant pressures, reversing valve and defrost controls.
2. 2Auxiliary heat staging is checked too, so the system isn't quietly relying on expensive backup heat.

What it is likely to cost

Thermostat and airflow fixes are inexpensive. Defrost boards, refrigerant leaks and reversing valves are larger repairs. You get the price before any work.

Diagnostic

$89

Defrost control board

From $349

Refrigerant leak / recharge

From $499

Reversing valve

From $699

Outdoor fan motor

From $449

Prices are starting points for standard work in the Savannah area. Final price depends on the system and site, and is confirmed before work begins. Permits and code-required upgrades may be additional.

Repair or replace?

Heat pumps run year-round, so they tend to reach end of life sooner than a separate AC and furnace — commonly around 12–15 years. A major repair near that age is worth comparing against replacement.

Questions people ask about this

Why does heat pump air feel cool?

Heat pump supply air is usually warm rather than hot — noticeably cooler than a gas furnace's. It can still heat the house well; it just runs longer to do it.

Should I switch to Emergency Heat?

Only as a short-term measure if the heat pump has failed. Emergency heat usually runs on electric resistance, which is expensive, and it doesn't fix the underlying problem.

Where to go next