Your aircon ran all summer without a hiccup, and now it won’t warm the lounge on a cold Perth morning. The culprit is usually simple: the wrong mode on the remote, a clogged filter, or a defrost cycle doing its job. Here’s how to tell, and when to call a technician.
Key Takeaways
- Remote settings, dirty filters, and the winter defrost cycle cause most heating failures; you can check all three in minutes.
Heating and cooling appliances account for about 40% of the energy use in the average Australian home (CHOICE).
Reversing valve and refrigerant faults need a licensed technician; WestOz Trades holds licence AU45143.
Start With the Two-Minute Checks
Heating and cooling appliances account for about 40% of the energy use in the average Australian home, according to CHOICE’s air conditioner buying guide. Grab the remote first: your unit only heats in heat mode (the sun symbol), with the set temperature a few degrees above the room’s.
Next, the filters: a clogged filter chokes airflow and is the top reason warm air feels weak. Our guide to how often you should service your air conditioner covers what servicing prevents.
| Symptom | Likely cause | What to do |
| Air blows but isn’t warm | Wrong mode or low set temp | Set heat mode, raise temp |
| Weak airflow, mild warmth | Clogged filter | Clean or replace the filter |
| Heating pauses, unit steams | Defrost cycle | Let the cycle finish |
| Cold air in heat mode | Stuck valve or low refrigerant | Call a licensed tech |
Steaming or Paused? It’s Probably the Defrost Cycle
Reverse cycle systems pull heat from the outside air, and on cold mornings the outdoor coil can ice up. Your unit pauses heating, melts the ice, and often steams while it works. That’s normal winter behaviour, not a fault.
If heating doesn’t resume, or the ice never clears, that’s one of the signs your air conditioner needs a professional service.
The Faults That Need a Licensed Technician
Still cold after the checks? You’re likely looking at a stuck reversing valve (the part that flips your system between cooling and heating), a refrigerant leak, or a failing sensor. None of these are DIY jobs. By law, a refrigerant handling licence is required for any work with a risk of refrigerant emission.
WestOz Trades holds licence AU45143 and runs 24/7 air conditioning repairs across Perth, with refrigeration mechanics doing the diagnosis.
Frequently Asked Questions
Usually the system isn’t actually in heat mode, or the set temperature sits below the room’s, so the unit idles. Dirty filters and the defrost cycle come next. If warm air still won’t come after those checks, book a technician to test the reversing valve and refrigerant.
Often the fan is just circulating air while the unit warms up, or the defrost cycle is thawing the outdoor coil. Cold air beyond a few minutes points to low refrigerant or a stuck reversing valve, which needs a licensed repair.
Yes. During defrost, melted ice meets warm components and rises as water vapour that looks like smoke. It passes quickly and heating resumes on its own. Steam is fine; smoke with a burning smell isn’t, so switch off and call a technician.
Cold House and No Luck? We’ll Sort It
Don’t spend another week in a cold house. Book a repair with WestOz Trades, or see what an air conditioning service includes before we arrive.
