Why Is My Air Con Blowing Hot Air? Common Causes and How to Fix It
When you switch on your air conditioner expecting a blast of cool air, the last thing you want is warm air blowing in your face. If your air con is blowing hot air, there’s usually an underlying issue that needs attention—ranging from simple cleaning to more serious mechanical faults.
Here’s what might be going wrong, how to fix it, and when to call a professional.
Quick Summary
| Issue | Common Signs | How to Fix It |
|---|---|---|
| Incorrect Thermostat Setting | Air con set to heat or fan only; air never cools | Check mode is on cool and lower the temperature setting |
| Dirty Air Filters | Weak airflow, musty smell, higher energy bills | Clean or replace filters every 4–6 weeks |
| Blocked Condenser Coils | Outdoor unit covered in dust or leaves; reduced cooling | Turn off power and gently hose down coils; clear debris |
| Low Refrigerant Levels | Hissing sounds, ice on pipes, longer cooling time | Requires licensed technician to detect and refill safely |
| Electrical or Sensor Faults | Air swings between warm and cool; unit shuts off | Call a professional to inspect wiring and components |
| Outdoor Unit Not Running | Indoor fan works but no outdoor activity | Check circuit breaker; remove obstructions; book service |
| General Lack of Maintenance | System underperforms, inconsistent temperatures | Schedule annual professional servicing before summer |
1. Incorrect Thermostat Setting
Before assuming something’s broken, double-check your thermostat.
If it’s accidentally set to “heat” or “fan only,” your system won’t cool. Even if it’s on “cool,” an incorrect temperature setting can still cause problems.
What to do:
- Make sure the mode is set to cool
- Lower the temperature a few degrees below room temperature
- Wait a few minutes to see if the air turns cold
If it’s still blowing warm air, move to the next steps.
2. Dirty Air Filters
Clogged filters block airflow and cause the system to overheat. When this happens, the indoor unit may stop cooling and push warm air instead.
Signs: Reduced airflow, higher energy bills, or a musty smell.
Fix: Remove and clean or replace your filters every 4–6 weeks during summer. Regular maintenance keeps the air fresh and your system efficient. Learn more with our blog: How to Clean Split System Filters
3. Blocked or Dirty Condenser Coils
The outdoor condenser releases heat from your home. When it’s coated in dirt, dust, or leaves, the system can’t release heat effectively—and ends up circulating warm air back inside.
Fix:
- Turn off power at the isolator switch
- Gently hose down the coils to remove debris
- Keep at least 30cm of clear space around the outdoor unit
If you notice ice, rust, or strange noises, it’s time to get a professional technician involved.
4. Low Refrigerant Levels
Refrigerant is the chemical that cools the air inside your split system. A leak or low refrigerant level means your air con can’t absorb heat, so it starts blowing warm air.
Warning signs:
- Hissing or bubbling sounds
- Ice forming on pipes
- Longer cooling times
Fix: Only a licensed refrigeration mechanic can safely locate and fix refrigerant leaks. Avoid DIY top-ups—they’re illegal and dangerous without proper certification.
5. Electrical or Sensor Faults
If your unit keeps switching from cool to warm, the issue might be electrical. Faulty wiring, a burnt capacitor, or a malfunctioning temperature sensor can interrupt the cooling cycle.
Fix: Don’t attempt electrical repairs yourself. Contact a professional who can test the connections and replace damaged components safely.
6. Outdoor Unit Not Running
If the indoor unit is working but the outdoor fan is silent, the compressor or fan motor might have failed—or the circuit breaker may have tripped.
Fix:
- Check the circuit breaker and reset if necessary
- Clear any obstructions near the outdoor unit
- If it still doesn’t start, call a technician to test the motor and capacitor
7. It’s Time for a Professional Service
If your air con is blowing hot air even after basic checks, your system might simply need a comprehensive service. During a professional service, technicians will:
- Inspect refrigerant levels
- Clean filters, coils, and drains
- Test electrical components
- Ensure your system is operating efficiently
Prevent Future Issues
- Clean filters regularly
- Keep outdoor units clear of debris
- Schedule annual servicing before summer
- Don’t delay repairs when performance drops
Routine maintenance not only prevents warm-air issues but also extends the lifespan of your air conditioner and reduces power bills.
Time for a New Split System Air-Con?
If your air conditioner keeps blowing hot air, struggles to cool, or needs frequent repairs, it might be time for a replacement. A new split system air conditioner can deliver better energy efficiency, quieter operation, and more reliable cooling—especially in Perth’s summer heat.
At Air-Cond Installs WA, we supply and install high-quality split systems designed to suit your home, preferred brand, and budget. From single-room setups to multi-head systems, our expert installers ensure your new unit is fitted correctly for maximum performance and longevity.
Ready to upgrade?
View our installation options, explore our brands, or contact us today to request a quote and enjoy cool, comfortable air all year round.
