Heat pumps are the workhorse of heating and cooling in New Zealand homes, but when they stop working it can be frustrating — especially in the middle of a cold Southland winter or a sweltering Northland summer. Before you call a technician, there are several straightforward checks you can do yourself. This guide walks you through the most common causes, what you can safely investigate, and when it is time to bring in a qualified professional.
Common Causes of a Heat Pump Not Working
Understanding why your heat pump has stopped — or is underperforming — is the first step to fixing it. The main culprits fall into a few broad categories:
- Age and wear — Components deteriorate over time. Capacitors, fan motors, and compressors all have a finite lifespan, and an older unit may simply be reaching the end of its serviceable life.
- Weather exposure — New Zealand's climate can be harsh. Coastal salt air accelerates corrosion on outdoor units, high UV degrades plastic components, and heavy rain or frost can interfere with operation. Units in exposed locations on the Kapiti Coast or Canterbury plains face particularly tough conditions.
- Poor original installation or workmanship — An incorrectly sized unit, poorly routed refrigerant lines, or inadequate electrical supply can cause problems that only become apparent months or years later.
- Lack of maintenance over the years — Dirty filters, blocked outdoor units, and low refrigerant levels are almost always the result of skipped servicing.
- Moisture-related issues — Condensate drain blockages, water ingress into the indoor unit, or high indoor humidity can all trigger faults or cause the unit to shut down on a safety cut-out.
Step-by-Step: What to Check First
Work through these checks before calling a technician. Many call-outs turn out to be simple fixes a homeowner can resolve safely.
1. Power and Settings
- Check the circuit breaker in your switchboard — heat pumps draw significant current and breakers can trip, especially on hot days when the compressor works hard.
- Confirm the unit is set to the correct mode (heat, cool, or auto) and that the temperature setpoint is actually calling for operation.
- Check the remote control batteries — a flat battery is a surprisingly common cause of a seemingly dead unit.
- Make sure the timer function has not been accidentally activated.
2. Filters and Airflow
Dirty filters are the single most common cause of reduced performance and nuisance shutdowns. Most manufacturers recommend cleaning filters every four to six weeks during heavy use. Remove the indoor unit's front panel, slide out the filters, and wash them gently with warm water. Allow them to dry fully before reinserting.
Outdoors, check that the outdoor unit is not blocked by overgrown shrubs, a fence, or accumulated leaves. The unit needs clear airflow on all sides.
3. Ice or Frost on the Outdoor Unit
Some frost on the outdoor unit during cold weather is normal — the unit runs a defrost cycle to clear it. However, if the unit is heavily iced over and not defrosting, this may indicate a refrigerant issue or a faulty defrost sensor, which requires a technician.
4. Error Codes
Most modern heat pumps display a fault code on the indoor unit or remote when something is wrong. Note the code and look it up in your owner's manual or the manufacturer's website. Common NZ brands include Mitsubishi Electric, Fujitsu, Daikin, Panasonic, and Hitachi — all publish fault code guides online.
5. Condensate Drain
If water is dripping from the indoor unit, the condensate drain may be blocked. This is a maintenance task most homeowners can manage: locate the drain outlet (usually outside or into a laundry tub) and clear any blockage with a thin brush or by flushing with water.
NZ Climate Considerations
New Zealand's varied climate means heat pumps face different challenges depending on where you live:
| Region | Key Challenge | What to Watch For |
|---|---|---|
| Northland / Auckland | High humidity, salt air | Corrosion on outdoor coil, mould in indoor unit |
| Wellington | High winds, coastal exposure | Debris ingress, vibration loosening fittings |
| Canterbury / Otago | Cold winters, frost | Icing on outdoor unit, reduced heating capacity |
| West Coast | Heavy rainfall, humidity | Condensate drain blockages, moisture ingress |
For coastal properties, consider having the outdoor unit's coil professionally cleaned and treated with a corrosion inhibitor annually.
Maintenance: The Best Prevention
Regular maintenance is the best way to prevent heat pump problems. A well-maintained unit will also run more efficiently, saving on power bills — relevant given New Zealand's electricity costs. Include heat pump servicing in your seasonal home maintenance checklist:
- Every 4–6 weeks (during use): Clean indoor filters.
- Annually: Professional service — coil clean, refrigerant check, electrical connections, condensate drain flush.
- Every 2–3 years: Full inspection of refrigerant charge and compressor performance.
For rental properties, the Healthy Homes Standards set minimum requirements for heating, and landlords must ensure heating devices are in good working order.
Compliance and Restricted Work
This is important: refrigerant handling is restricted work in New Zealand. Under the Ozone Layer Protection Act and industry regulations, only a certified refrigeration technician (holding a relevant refrigerant handling licence) may legally purchase, handle, or recharge refrigerants such as R32 or R410A. Attempting to top up refrigerant yourself is illegal and potentially dangerous.
Similarly, any electrical work on the heat pump's wiring — including the dedicated circuit from the switchboard — is restricted electrical work that must be carried out by a registered electrician. Check the Electrical Workers Registration Board (EWRB) to verify a sparky's registration before they start work.
If your heat pump installation requires a building consent (for example, significant penetrations through an external wall in certain situations), check with your local council. Many standard heat pump installations fall under Schedule 1 exemptions, but always confirm with your council — requirements vary.
For guidance on energy efficiency and choosing the right heat pump size, Energywise provides excellent NZ-specific advice.
When to Call a Professional
Call a qualified heat pump technician if:
- The unit displays a fault code you cannot resolve with the owner's manual.
- There is no cooling or heating output despite the unit appearing to run.
- You suspect a refrigerant leak (hissing sound, ice on refrigerant lines, sudden loss of performance).
- The problem is recurring after you have cleaned filters and checked power.
- The unit is making unusual noises — grinding, rattling, or banging — which can indicate a failing compressor or fan motor.
- Water is leaking inside the home from the indoor unit.
- The unit is more than 10–15 years old and performance has declined significantly — it may be more cost-effective to replace than repair.
A qualified tradesperson can diagnose the root cause and recommend the right solution. You can find licensed local heat pump technicians and electricians on tradedirectory.co.nz.
DIY vs Professional: Quick Summary
| Task | DIY OK? | Notes |
|---|---|---|
| Clean indoor filters | ✅ Yes | Do every 4–6 weeks |
| Clear outdoor unit of debris | ✅ Yes | Keep 300–500 mm clearance |
| Check breaker and remote batteries | ✅ Yes | First thing to check |
| Clear condensate drain | ✅ Yes | Use care, follow manual |
| Recharge refrigerant | ❌ No | Licensed technician only |
| Electrical wiring work | ❌ No | Registered electrician only |
| Coil cleaning (chemical) | ⚠️ Caution | Best left to a technician |
| Fault diagnosis and repair | ❌ No | Qualified technician required |
Sources & Further Reading
- Energywise — Heat Pumps — NZ guidance on heat pump efficiency and sizing
- BRANZ — Building Research Association of NZ, technical guidance on moisture and ventilation
- Electrical Workers Registration Board (EWRB) — Verify your electrician's registration
- Tenancy Services — Healthy Homes — Heating requirements for rental properties
- WorkSafe NZ — Safety information for working around electrical and refrigeration systems
- MBIE Building Performance — NZ Building Code and consent information
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