Heat pump not heating? 8 common causes and what to do

Start here: the two-minute checks

Before assuming the worst, run through these. A good share of “broken” heat pumps are one of the first three.

1. It’s in the wrong mode

Sounds obvious, and it’s genuinely one of the most common callouts we get. Check the remote shows Heat (a sun icon), not Cool, Dry or Fan. If someone else has used the remote, or the batteries were changed, the mode can reset.

2. The temperature is set too low

If the set point is below room temperature, the unit has nothing to do. Set it to 21–22°C and see whether it kicks in.

3. Filters are clogged

Blocked filters choke airflow. The unit may be producing heat but can’t move it into the room, so it feels like weak or no output. Open the front panel, slide the filters out, wash them in warm water, dry fully, refit. Do this every couple of months — it’s the single most useful thing you can do for a heat pump.

4. It’s in defrost mode

On cold, damp mornings frost forms on the outdoor coil, and the unit periodically reverses to melt it. During defrost the indoor fan stops and you get no heat — sometimes steam off the outdoor unit. This is normal and lasts a few minutes. If it seems to be defrosting constantly, that’s worth a look.

5. The outdoor unit is blocked or dirty

The outdoor unit needs airflow. Vegetation grown across it, stacked boxes, a fence built too close, or a coil packed with leaves and dust all strangle performance. Clear at least 30cm around it and gently clear debris off the fins.

6. Low refrigerant charge

A heat pump is a sealed system — it shouldn’t lose refrigerant. If it’s low, there’s a leak. Symptoms are gradually weakening heat over weeks or months, and sometimes ice on the pipework. This is not a top-up-and-forget job: the leak needs finding and fixing, and handling refrigerant requires the right ticket. Call someone.

7. A failed capacitor, fan or reversing valve

If the outdoor unit hums but the fan doesn’t spin, a capacitor is a common culprit. If the unit cools fine but won’t heat, the reversing valve — the component that flips the system between heating and cooling — is a prime suspect. Both are diagnosable and usually repairable.

8. An error code or a tripped breaker

Flashing lights on the indoor unit are the system telling you what’s wrong — the pattern maps to a fault code in the manual. Also check your switchboard: a tripped breaker means no power, and a breaker that trips repeatedly means an electrical fault that needs investigating rather than resetting.

When it’s worth repairing

Most faults on a unit under about 10 years old are worth fixing — capacitors, fans, sensors, valves and controls are all replaceable, and a repair typically costs a fraction of a new system. Where we’d steer you toward replacement is a 12–15+ year old unit with a major failure like a compressor, or a system that keeps failing repeatedly. We’ll give you the honest call either way.

Still not heating after the checks above? Book a repair and we’ll diagnose it properly — fault found first, clear price before any work.