AC not heating in winter

A reverse-cycle air conditioner that won't heat may be in the wrong mode, running a defrost cycle, or have dirty filters, a faulty valve or refrigerant problems. Check the settings and filters first, then book a service if it still blows cold.

There's no one-size-fits-all answer for AC not heating in winter: every home is different. Western Sydney's hot summers and sudden storms add to the wear on anything exposed to the weather. In Blacktown City, cold winter mornings and hot summer afternoons, plus seasonal movement in clay soils are part of the picture, along with how old the home is and how it was built.

Below you'll find the diagnostic context for AC not heating in winter in this region, the warning indicators worth acting on early, the standards-compliant repair process, the main things that drive the price, and the NSW Fair Trading licensing reference points — enough information to engage an air conditioning specialist on confident terms.

Why it happens

Reverse-cycle air conditioners heat by extracting heat from the outdoor air, which gets harder as the temperature drops. On cold mornings, frost can build up on the outdoor coil and block airflow, so the unit pauses heating while it runs a defrost cycle. A system with a low refrigerant charge, a dirty outdoor coil or a faulty reversing valve will struggle to heat sooner, and on milder days, than a well-maintained one.

Warning signs

Catching AC not heating in winter early — at the warning-sign stage — usually keeps the repair smaller and cheaper than waiting for a failure. The signals worth taking seriously:

• Warm air blowing from AC on cooling mode
• Ice forming on indoor or outdoor unit
• Unusual noises (rattling, grinding, banging)
• Water dripping from indoor unit
• AC running constantly but not reaching set temperature
• Significantly higher power bills in summer

If any of these patterns sound familiar, don't wait for the next storm season or heatwave to force the issue. Ask for an assessment and a written quote before any work starts, and check whether the inspection itself is charged.

What happens if you leave it

The risk of leaving AC not heating in winter alone is that the conditions behind it don't pause. Clay soils keep moving, the seasons keep cycling, storms keep arriving — and the problem keeps developing alongside them. The cost curve can be steep: dealing with it early usually costs much less than dealing with the same problem after months of neglect.

On top of the cost escalation, if it's left until the next storm or heatwave, the failure tends to happen at the worst possible moment. There's an insurance dimension as well: insurers can reduce or decline claims where the damage stems from a pre-existing issue the homeowner could have addressed. A documented assessment by an air conditioning specialist both directs the repair and creates a paper trail your insurer will recognise.

How an air conditioning specialist usually fixes this

Resolving AC not heating in winter properly follows a clear sequence. The work should use materials and fixings suited to the home's exposure to heat, sun and wind, and the same logical structure applies whether the home is in an established suburb like Oakhurst or a growth area like Schofields:

1. Load Calculation. Correct sizing is critical. Your technician calculates the cooling/heating load for each room or zone based on volume, insulation, and window orientation.
2. Installation Planning. Indoor and outdoor unit placement is planned for efficiency, low noise near neighbours, and compliance with planning and noise rules.
3. Licensed Installation. Refrigerant handling requires an ARC licence and electrical connections require a licensed electrician — ask the installer how both are covered.
4. Commission & Test. The system is commissioned and tested across all modes, with a full handover explaining operation, filter cleaning, and recommended service intervals.

Following this sequence ensures the work resolves the actual driver of AC not heating in winter — not just the surface symptom — and that everything is documented to the standard your insurer (and any future buyer's conveyancer) will expect to see.

How jobs are usually priced

Pricing for AC not heating in winter varies with the scope of work, the access conditions on site, which materials are required, and how far the issue has progressed. Older homes can add cost if hidden damage or outdated components turn up once work starts, so ask how any extra work will be priced before you agree to go ahead.

Minor repair

Call-out + parts

Moderate work

Supply + install

Major project

Inspect, then quote

Price depends on the system type and capacity, the brand, the distance between the indoor and outdoor units, the electrical work needed, wall construction and roof space access. Ducted systems also vary with zones and ductwork. Ask for the unit model and installation details in the quote.

A written quote with a clear scope of works is your protection here. Don't accept a verbal price for AC not heating in winter — if there's a disagreement later, the written scope is what everyone will refer back to.

Licences and rules in NSW

Air conditioning and refrigeration work is specialist work in NSW, so it needs a licence from NSW Fair Trading whatever the job's value. Technicians who handle refrigerant also need an ARC refrigerant handling licence (ARCtick), and electrical connections must be done by a licensed electrician. Verify both before engaging a contractor.

These government websites explain the rules and let you check a licence:

• NSW Fair Trading – Refrigeration & AC Licence
  Verify your AC technician holds a current NSW refrigeration and air conditioning licence.
• ARC Tick – Refrigerant Handling Licence
  Technicians handling refrigerants must hold an ARC licence — verify before they work on your AC system.
• Energy NSW – AC Efficiency Rebates
  NSW Government rebates available for upgrading to energy-efficient air conditioning systems.
• Endeavour Energy – Electricity Network
  Endeavour Energy runs the electricity network in Blacktown City — your electrician deals with it if an installation needs changes to your connection.

Hiring an unlicensed tradie for AC not heating in winter when the job needs a licence might look cheaper on the day, but it can cost far more later. Insurers may not cover resulting damage, the work may have to be redone, and getting defects fixed is harder. If you're unsure whether the work needs a licence, ask the tradie and check with NSW Fair Trading.

Common questions

• Why do reverse-cycle air conditioners stop heating effectively in Blacktown winters?

  Reverse-cycle systems extract heat from the outdoor air and transfer it inside. As the outdoor temperature drops, there's less heat to extract, so heating output and efficiency fall, and the unit periodically pauses heating to defrost the outdoor coil. Dirty coils and filters make this worse, so the system starts to struggle on milder days than it should. Have the system serviced before winter, and if it stops heating for long periods on cold mornings, ask a technician to check the defrost operation.

• What heating alternative should I use if my AC isn't heating in Blacktown?

  Electric panel heaters and oil column heaters are practical backup options — they don't need venting and are available at hardware stores. Keep any portable heater well clear of curtains, bedding and furniture, and never leave it running unattended. Portable gas heaters need adequate ventilation. For longer-term heating, an extra heater dedicated to the coldest rooms can provide backup during service periods. Reverse-cycle air conditioners remain one of the most energy-efficient ways to heat a home, so keeping yours serviced and running efficiently is the best long-term strategy.

• What temperature should I set my reverse-cycle heater to in Blacktown?

  Government energy-saving advice generally recommends a moderate heating setting of around 18–20°C, as every extra degree adds to running costs. Setting the heating very high doesn't warm the room faster; it just makes the system work harder for longer. A well-maintained reverse-cycle unit that's correctly sized for the room should comfortably hold a moderate temperature on a typical winter day. If it can't, even on milder days, a fault or maintenance issue is likely.