If your heat pump smells musty or sour when it starts, blows out black specks or makes your eyes and nose itch, the problem is usually inside the unit, behind the filters. Moisture condenses on the indoor coil every time the unit cools or dries the air, and dust sticks to that wet surface. Over time it becomes a layer of grime and mould on the coil fins and the long cylindrical fan, known as the fan barrel.
A heat pump deep clean removes that layer. We protect the wall and floor, strip the indoor unit back, and wash the coil, fan barrel, drain tray and drain line with a purpose made cleaning solution and a contained wash kit. This is different from routine heat pump servicing, which is a regular check up. Cleaning is the fix when there is already a smell, visible mould or a dirty airflow.
Pricing: every job starts with a free in-home assessment and a written quote, with a fixed price agreed before any work starts.
Want the whole system checked as well as cleaned? See heat pump servicing.
Why heat pumps grow mould
A heat pump in cooling or dry mode pulls moisture out of the air by chilling the indoor coil. That water should run into the drain tray and outside. But the coil stays damp for a while after the unit stops, the inside of the unit is dark, and the air passing through carries dust, skin flakes, cooking residue and pet hair. That is exactly what mould needs.
Filters catch the bigger particles, but fine dust still gets through, especially if the filters have been left for a few months. Consumer NZ notes that mould on the outer panels can simply be wiped off, but mould on the fins or filters probably means it is growing inside the unit, and recommends a professional clean rather than a DIY attempt, because scrubbing it at home can spread spores through the house.
Signs your heat pump needs a deep clean
These are the signs that point to a dirty coil or fan barrel rather than a mechanical fault. If the unit is not heating at all or shows an error code, that is a repair, not a cleaning job.
- A musty, damp or sour smell when the heat pump starts
- Black spots or slime visible on the louvres or the fan barrel behind them
- Dust or black specks blowing out with the air
- Weak airflow that does not improve after you clean the filters
- Water spitting from the vents or dripping from the indoor unit
- Allergy or asthma symptoms that get worse when the heat pump runs
How It Works
What our deep clean includes
A deep clean takes around one and a half to two hours per high wall unit. We photograph the coil and fan barrel before and after so you can see the difference.
- Drop sheets and a fitted wash bag so dirty water goes into a bucket, not on your wall
- Remove the front panel, filters and louvres and wash them by hand
- Apply a coil cleaner suited to heat pump coils, then rinse the coil fins
- Wash the fan barrel blade by blade, where most of the smell usually lives
- Clean the drain tray and flush the drain line to clear sludge and blockages
- Reassemble, run the unit and check drainage, airflow and operation
- Before and after photos, plus a short note on anything else we noticed
Cleaning cost and how often you need it
Heat pump cleaning is quoted free, with a fixed price per unit agreed before we start. Ceiling cassettes and ducted systems need a different method and are quoted after we see the unit. If you have several units, we clean them in one visit.
Most homes do not need a deep clean every year. If you clean your filters regularly, a deep clean every few years is often enough. Units that run a lot in cooling or dry mode, sit in bedrooms, or serve someone with asthma or allergies may need one more often. Gen Less recommends cleaning filters monthly through winter, which is the best way to slow the build up between cleans.
Auckland humidity and heat pump mould
Auckland is humid for much of the year, and many households use their heat pump on dry mode to deal with damp air and condensation. That is a sensible use of the unit, but it keeps the coil wet. Combine that with homes where moisture from cooking, showers and drying clothes has nowhere to go, and the inside of a heat pump becomes a reliable place for mould to grow.
A clean unit is only part of the answer. If the house itself is damp, with wet windows every morning and mould in corners, cleaning the heat pump will help the air it blows, but the damp will keep coming back. In those homes we look at the whole picture, including extractor fans and home ventilation systems.
Keeping it clean afterwards
A few habits make a real difference. Clean the filters with a vacuum or warm water and let them dry fully before refitting. After a long session in cooling or dry mode, run the fan on its own for a while to help dry the coil. Keep the room ventilated and avoid drying washing right under the unit.
Watch for the smell coming back. If it does, it is far easier to deal with early. We can also add a deep clean to a regular service visit so it happens on a schedule rather than after the smell returns.
Why Choose Cheeky's Heat Pumps for Heat Pump Cleaning
Proper wash kit
A fitted wash bag and drop sheets keep dirty water off your walls, carpet and furniture.
Before and after photos
You see the coil and fan barrel before and after, so you know exactly what was removed.
Fan barrel cleaned properly
We clean the fan barrel, not just the coil face, because that is where most smells start.
Honest advice on damp
If the real problem is a damp house, we tell you, rather than selling a clean every year.
Heat Pump Cleaning FAQs
Why does my heat pump smell musty?
Usually because mould and grime have built up on the wet indoor coil and fan barrel. Cleaning the filters will not reach it. A deep clean removes the build up that causes the smell.
Is mould in a heat pump a health risk?
Mould spores can irritate the airways and are a known trigger for people with asthma and allergies. If you can see mould on the fins or fan, Consumer NZ advises getting a professional clean rather than tackling it yourself.
How is cleaning different from servicing?
Servicing is routine preventive maintenance with checks and a performance test. Cleaning is a deep wash of the coil, fan barrel and drain to remove mould and dirt that have already built up.
Can I clean the coil with a spray from the hardware store?
Some coil sprays can clean the front of the coil, but they do not reach the fan barrel and can leave residue or push dirty water into the drain tray. For visible mould, a full deep clean is more effective.
How long does a deep clean take?
Around one and a half to two hours for a standard high wall unit. The unit can be used straight after.
Will cleaning lower my power bill?
A clogged coil and fan reduce airflow, so the unit works harder for the same heat. Restoring airflow can help efficiency, although the size of any saving depends on how dirty the unit was.
Heat Pump Cleaning Near You
Find your region or suburb for local heat pump cleaning information:
Related Heat Pump Services
Heat Pump Cleaning Guides
- How to Clean Your Heat Pump Filter (and When to Call a Pro)
- Heat Pump Leaking Water Inside? Causes and Fixes
See the heat pump prices guide or every service we offer.