⚡ Electrical Tips

Air Conditioner Not Cooling? Common Causes and Fixes (Brisbane 2026)

20 min readUpdated Jul 2026ARAaron · Licensed Electrician 1500996
⚡ The Quick Answer

AC running but not cooling? See the 8 most common causes and fixes from a local Capalaba electrician. Dirty filters, refrigerant leaks, compressor issues — all explained.


Your air conditioner is running but not cooling your Brisbane home? You’re not alone. In Brisbane’s brutal summer humidity, a struggling AC is more than just uncomfortable — it’s unbearable. At Amplus Electrical & Air, we’ve diagnosed and fixed hundreds of “AC not cooling” problems across Capalaba, Cleveland, and the Redlands.

Most of the time, the problem is fixable without replacing the whole unit. In this guide, I’ll walk you through the most common causes, what you can check yourself, and when to call a licensed technician. I’ll also share real examples from jobs we’ve done so you can see what to expect.

Split system air conditioner in Brisbane home
A split system struggling to keep up — common in Brisbane’s humidity

Brisbane Climate: Why Your AC Works Harder Here

Brisbane’s subtropical climate puts unique stress on air conditioners. Understanding these factors helps you diagnose problems faster and prevent them:

Humidity (60-80% in Summer)

The impact: High humidity means your AC works twice as hard — it’s cooling the air AND removing moisture. This puts extra strain on the compressor and can lead to:

What to do: Use the “dry” mode on your AC during humid days. This removes moisture without overcooling. Clean filters monthly during summer to prevent mould buildup. For more tips on efficient cooling, see the Australian Government’s heating and cooling guide.

Salt Air (Coastal Suburbs)

The impact: If you live in Cleveland, Victoria Point, Wynnum, or anywhere near the bay, salt air corrodes the outdoor unit’s copper coils and electrical components. This causes:

What to do: Rinse the outdoor unit with fresh water every 3 months. Consider a marine-grade protective coating when installing a new unit. Check for corrosion during annual servicing.

Storms and Power Surges

The impact: Brisbane’s summer storms (November-February) bring lightning and power surges that can:

What to do: Install a surge protector ($150-$300). During storms, turn off the AC at the isolator switch. If your AC stops working after a storm, check the circuit breaker first. Energex has a storm safety guide with more information.

Extreme Heat (35°C+ Days)

The impact: On extreme heat days, your AC runs at maximum capacity for hours. This can cause:

What to do: Don’t set the temperature below 24°C on extreme days — the AC won’t cool faster, it’ll just work harder. Make sure the outdoor unit has shade (but not blocked airflow). Service the AC before summer starts.

Seasonal Patterns: When AC Problems Spike in Brisbane

Understanding seasonal patterns helps you catch problems early:

For a detailed breakdown of common AC problems and fixes, see our guide on split system installation costs in Brisbane.

Spring (September-October): The Wake-Up Call

Common problems:

What to do: Clean filters, run the AC on fan mode for 30 minutes to clear dust, check the outdoor unit for winter debris. Book a service before the summer rush.

Summer (November-March): Peak Stress

Common problems:

What to do: Clean filters every 4-6 weeks. Keep the outdoor unit shaded and clear of debris. If the AC stops cooling, turn it off and call us immediately — running a struggling AC can cause expensive damage.

Autumn (April-May): The Relief

Common problems:

What to do: Book a service to address any summer wear. This is the best time for repairs — we’re less busy and can give your AC attention before next summer.

Winter (June-August): Heating Mode

Common problems:

What to do: Clean filters before switching to heating mode. If the AC hasn’t been serviced in 12+ months, book one now — winter is our quietest season.

DIY vs. Professional Troubleshooting: What You Can Safely Check

Some checks are safe for homeowners. Others require a licensed technician. Here’s the breakdown:

✅ Safe DIY Checks (No Licence Required)

Check How to Do It Time Cost
Air filters Open front panel, remove filters, wash with warm soapy water, dry completely, reinstall 15 minutes $0
Outdoor unit debris Turn off power, remove leaves/dirt from around unit, gently hose coils from inside out 20 minutes $0
Thermostat settings Check mode is set to “cool”, temperature is set below room temp, replace remote batteries 2 minutes $5 (batteries)
Circuit breaker Check switchboard, reset if tripped 2 minutes $0
Isolator switch Check the switch next to outdoor unit is turned on 1 minute $0
Vents (ducted systems) Walk around house, ensure all vents are open and unblocked 5 minutes $0

❌ Professional Only (Licence Required)

Problem Why You Need a Pro Typical Cost
Refrigerant leak Illegal to handle without ARCtick licence. Requires specialised equipment to find and fix leaks. $250-$500
Compressor failure High-voltage electrical work. Requires refrigerant handling to test and recharge. $500-$1,500
Electrical faults High-voltage components. Risk of electrocution or fire if done incorrectly. $150-$300
Circuit board replacement Requires electrical licence and technical knowledge of AC systems. $300-$600
Fan motor replacement Electrical work + mechanical disassembly. Risk of injury if done incorrectly. $250-$500
Thermostat wiring issues Low voltage but still electrical work. Incorrect wiring can damage the AC. $150-$300

Why it matters: DIY electrical or refrigerant work is illegal in Queensland, voids your warranty, and can be dangerous. We’ve seen homeowners cause $2,000+ in damage trying to save $150 on a repair.

When in doubt, call us. We’ll tell you over the phone if it’s something you can handle yourself.

Cost Breakdown: What Each Problem Costs to Fix

Here’s what you can expect to pay for the most common “AC not cooling” problems:

Problem DIY Cost Professional Cost Time to Fix
Dirty filters $0 $150-$225 (service call) 15 min (DIY) / 1 hour (pro)
Dirty outdoor coils $0 $150-$250 20 min (DIY) / 1-2 hours (pro)
Thermostat batteries $5 $150 (service call) 2 min (DIY)
Thermostat replacement Not recommended $150-$300 1 hour
Refrigerant leak Illegal $250-$500 2-3 hours
Compressor failure Not recommended $500-$1,500 (or $1,600-$3,500 for new unit) 2-4 hours
Electrical fault Not recommended $150-$300 1-2 hours
Circuit board replacement Not recommended $300-$600 1-3 hours
Blocked drain pipe $0 (vacuum/wire) $150-$250 30 min (DIY) / 1 hour (pro)
Undersized unit Not fixable $1,600-$3,500 (replacement) 4-6 hours

Key insight: The cheapest fixes are the ones you can do yourself (cleaning filters, clearing debris). The expensive ones require a licensed technician (refrigerant, electrical, compressor). That’s why regular maintenance matters — it catches small problems before they become expensive ones.

Emergency vs. Non-Emergency: When to Call Immediately

Not all “AC not cooling” problems are emergencies. Here’s how to prioritise:

🚨 Call Immediately (Same-Day Service)

What to do: Turn off the AC at the isolator switch. Call us immediately on 0419 014 146.

⚠️ Call Within 24-48 Hours

What to do: Turn off the AC if ice is forming. Call us to book a service.

📅 Call Within a Week

What to do: Book a service at your convenience. These problems won’t cause immediate damage but will get worse over time.

Repair vs. Replace: How to Decide

When your AC stops cooling, you need to decide: repair the existing unit or replace it? Here’s a decision framework. If you’re leaning toward replacement, our split system vs ducted air conditioning guide breaks down the costs and benefits of each option.

Repair When:

Replace When:

The Maths: Repair vs. Replace

Example 1: 8-year-old unit needs compressor replacement

Example 2: 14-year-old unit needs compressor replacement

Example 3: 10-year-old unit needs refrigerant leak repair

Our advice: If you’re unsure, we’ll give you an honest assessment. We’d rather recommend a replacement than charge you for a repair that won’t last. That’s how we’ve built trust across the Redlands.

Why Your Air Conditioner Is Running but Not Cooling

When your AC is blowing air but the room isn’t getting cool, there’s usually one of these culprits:

1. Dirty or Blocked Air Filters (Most Common)

The problem: Clogged filters restrict airflow, so your AC can’t circulate enough cool air. This is the #1 cause of poor cooling performance.

How to check: Open the front panel of your indoor unit and pull out the filters. If they’re covered in dust, hair, or grime, they need cleaning.

The fix: Wash the filters with warm soapy water, rinse thoroughly, and let them dry completely before reinstalling. Do this every 1–3 months during summer.

Cost if you do it yourself: $0

Cost if we do it for you: $120–$180 (part of a service call). See our AC repair cost guide for more pricing.

2. Dirty Outdoor Coils

The problem: The outdoor unit (condenser) releases heat from your home. If the coils are clogged with dirt, leaves, or debris, the unit can’t shed heat efficiently, so it struggles to cool.

How to check: Look at the outdoor unit. If the metal fins on the back or sides are covered in dirt, dust, or plant matter, they need cleaning.

The fix: Turn off the power, then gently hose down the coils from the inside out. Don’t use a pressure washer — the fins are delicate. For heavy buildup, we use specialised coil cleaners.

Cost if you do it yourself: $0 (just your time)

Cost if we do it for you: $150–$250

3. Low Refrigerant (Gas Leak)

The problem: Refrigerant is what actually cools the air. If there’s a leak, the system loses pressure and can’t cool properly. You might notice ice forming on the indoor or outdoor unit.

How to check: Look for ice on the copper pipes or the indoor/outdoor units. Listen for hissing sounds (though most leaks are silent). If your AC was working fine and suddenly stopped cooling, a leak is likely.

The fix: A licensed technician (ARCtick certified) must find the leak, repair it, then vacuum and regas the system. You can’t just top up the gas — the leak must be fixed first.

Cost: $250–$500 depending on the leak location and refrigerant type

Important: If your AC needs regassing more than once every few years, there’s a persistent leak. It might be more cost-effective to replace the unit. Only ARCtick-certified technicians can legally handle refrigerant — see ARCtick’s licensing requirements.

4. Thermostat Issues

The problem: The thermostat controls when the AC turns on and off. If it’s faulty, miscalibrated, or in the wrong mode, the AC won’t cool properly.

How to check: Make sure the thermostat is set to “cool” mode (not “fan” or “dry”). Check that the temperature setting is lower than the current room temperature. If the display is blank or unresponsive, the thermostat might be dead.

The fix: Replace the remote batteries. If the thermostat itself is faulty, we can replace it. For ducted systems, we might need to recalibrate or replace the central thermostat.

Cost: $150–$300 depending on whether it’s a simple battery replacement or a full thermostat replacement

5. Blocked or Closed Vents (Ducted Systems)

The problem: If your ducted AC has blocked or closed vents, airflow is restricted and the system can’t cool effectively.

How to check: Walk around your home and check every vent. Make sure they’re open and not blocked by furniture, curtains, or rugs.

The fix: Open all vents and clear any obstructions. If the problem persists, there might be a blockage in the ductwork itself.

Cost if you do it yourself: $0

Cost if we need to clear ducts: $200–$400

6. Undersized Unit

The problem: If your AC is too small for the space it’s trying to cool, it will run constantly but never reach the desired temperature. This is common when homeowners buy a cheap, small unit for a large room.

How to check: If your AC runs non-stop but the room never gets cool (especially on hot days), it’s probably undersized. Check the kW rating against your room size:

The fix: Replace the unit with a properly sized one. We can assess your space and recommend the right size. The Energy Rating Calculator can help you work out the right size for your room. See our guide on air conditioner installation costs for pricing.

Cost: $1,600–$3,500 for a new, properly sized unit including installation. See our AC installation cost guide for pricing.

7. Compressor Failure

The problem: The compressor is the heart of your AC — it pumps refrigerant through the system. If it fails, the AC won’t cool at all.

How to check: The outdoor unit might be making unusual noises (buzzing, clicking, or grinding), or it might not turn on at all. The unit might also trip the circuit breaker repeatedly.

The fix: Compressor replacement is expensive. If your unit is more than 10 years old, we usually recommend replacement instead of repair.

Cost: $500–$1,500 for compressor replacement, or $1,600–$3,500 for a new unit

8. Electrical Issues

The problem: Faulty wiring, a tripped circuit breaker, or a blown fuse can prevent the AC from running properly.

How to check: Check your switchboard — has the circuit breaker for the AC tripped? Is the isolator switch next to the outdoor unit turned on?

The fix: Reset the circuit breaker. If it trips again immediately, there’s a fault and you need to call a licensed electrician. We can diagnose and repair electrical issues.

Cost: $150–$300 depending on the fault

What You Can Check Yourself (Before Calling a Technician)

Before you call us, run through this checklist:

  1. Check the filters: Are they dirty? Clean them.
  2. Check the outdoor unit: Is it blocked by leaves, dirt, or plants? Clear the area and hose down the coils.
  3. Check the thermostat: Is it set to “cool” mode? Is the temperature setting lower than the room temperature? Replace the remote batteries.
  4. Check the vents (ducted systems): Are they open and unblocked?
  5. Check the circuit breaker: Has it tripped? Reset it.
  6. Check the isolator switch: Is it turned on?

If you’ve done all of this and the AC still isn’t cooling, it’s time to call a licensed technician.

When to Call a Licensed Technician

Call us if:

Real Examples: “AC Not Cooling” Jobs We’ve Fixed in the Redlands

Example 1: Dirty Filters in Capalaba

The problem: Customer’s 3-year-old split system was running but the bedroom wasn’t getting cool. Room temperature stayed at 28°C even when set to 22°C.

What we found: The filters were completely blocked with dust and pet hair. The outdoor coils were also clogged with dirt and leaves.

The fix: We deep-cleaned the filters and outdoor coils. We also checked the refrigerant levels — they were fine.

The cost:

Lesson: Clean your filters every 1–3 months. It’s the easiest and cheapest way to keep your AC running efficiently.

Example 2: Refrigerant Leak in Cleveland

The problem: Customer’s 7-year-old split system was blowing air but not cooling. They noticed ice forming on the outdoor unit’s copper pipes.

What we found: A small corroded spot on the outdoor coil was causing a slow refrigerant leak. The system was low on gas.

The fix: We repaired the corroded spot, vacuumed the system, and regassed it with the correct amount of refrigerant. We pressure-tested the system to confirm the leak was fixed.

The cost:

Lesson: If your AC needs regassing more than once every few years, there’s a persistent leak. It might be time to replace the unit.

Example 3: Undersized Unit in Alexandra Hills

The problem: Customer installed a 2.5kW split system in their 45m² lounge room. The AC ran constantly but the room never got below 26°C on hot days.

What we found: The unit was too small for the space. A 2.5kW unit is only suitable for rooms up to 20m². The lounge needed a 5kW unit.

The fix: We removed the undersized unit and installed a properly sized 5kW split system. The room now cools quickly and efficiently.

The cost:

Lesson: Always size your AC to match your room size. An undersized unit will run constantly, waste energy, and never cool properly.

Example 4: Thermostat Issue in Thornlands

The problem: Customer’s ducted AC was running but the house wasn’t cooling. The thermostat display was blank.

What we found: The thermostat had died. It wasn’t sending signals to the AC unit, so the system was running in default mode (which wasn’t cooling effectively).

The fix: We replaced the faulty thermostat with a new programmable model. The system now responds correctly to temperature settings.

The cost:

Lesson: If your thermostat display is blank or unresponsive, try replacing the batteries first. If that doesn’t work, the thermostat itself might need replacing.

Example 5: Compressor Failure in Victoria Point

The problem: Customer’s 14-year-old split system was making a loud buzzing sound and not cooling. The outdoor unit was vibrating excessively.

What we found: The compressor had failed. It was drawing excessive current and making abnormal noises.

The assessment: A new compressor would cost $900–$1,200. The unit was 14 years old and using R22 refrigerant (expensive and being phased out). We recommended replacement instead of repair.

The outcome: Customer replaced the old unit with a new 5kW inverter split system for $2,800. The new unit is quieter, more efficient, and comes with a 5-year warranty.

Lesson: If your AC is more than 10 years old and needs a major repair (like compressor replacement), it’s usually more cost-effective to replace the whole unit.

How to Prevent “AC Not Cooling” Problems

Most air conditioning problems can be prevented with regular maintenance. Here’s a maintenance schedule for Brisbane’s climate:

Monthly (Summer: November-March)

Every 3 Months (Year-Round)

Annually (Before Summer: October)

Every 2 Years

As Needed

The cost of prevention: $150-$250 per year for annual servicing.

The cost of neglect: $500-$1,500 for major repairs, or $2,800+ for premature replacement.

The maths is simple: Regular maintenance saves you money. It also keeps your AC running efficiently, which saves on energy bills.

Read our guide on split system running costs in Brisbane for more efficiency tips.

Why Choose Amplus Electrical & Air for AC Repairs?

1. Licensed and ARCtick Certified

We’re fully licensed electricians AND hold an ARCtick licence for refrigerant handling. We can diagnose and repair any type of air conditioner legally and safely. We’re also one of the top AC installers in Brisbane if you need a new system.

2. Transparent Pricing

We charge a flat $150/hour with no call-out fee. We’ll give you a quote before starting any repair work.

3. Honest Advice

If a repair isn’t worth it, we’ll tell you. We’d rather recommend a replacement than charge you for a repair that won’t last. That’s how we’ve built trust across the Redlands.

4. Same-Day Service

Most AC repairs can be done same-day or next-day. Call us in the morning, and we’ll usually have it sorted by the afternoon.

5. All Brands

We repair all major brands — Mitsubishi Electric, Daikin, Haier, Panasonic, Samsung, LG, and more. We carry common parts in our van so most repairs are completed in one visit.

Frequently Asked Questions

Why is my AC running but not cooling?

The most common causes are dirty filters, low refrigerant, dirty outdoor coils, or a faulty compressor. Start by checking and cleaning the filters. If that doesn’t fix it, call a licensed technician.

How often should I clean my AC filters?

Every 1–3 months during summer, or more often if you have pets or live in a dusty area. Clean filters are the easiest way to keep your AC running efficiently.

How much does it cost to fix an AC that’s not cooling?

Depending on the problem, it costs $150–$600. Simple fixes like cleaning filters or replacing a thermostat cost $150–$300. Refrigerant leaks cost $250–$500. Compressor replacement costs $500–$1,500.

Can I fix my AC myself?

You can clean filters and clear debris from the outdoor unit yourself. Anything else — refrigerant, electrical, compressor — requires a licensed technician. DIY repairs are illegal and dangerous.

How long do air conditioners last?

Quality split systems last 10–15 years with regular maintenance. Premium brands like Mitsubishi Electric and Daikin can last 15–20 years.

Is it worth repairing an old air conditioner?

If the unit is more than 10 years old and the repair costs more than 50% of a new unit, it’s usually better to replace it. We’ll give you honest advice about whether repair or replacement makes sense.

Why is ice forming on my AC?

Ice usually means low refrigerant (a leak) or restricted airflow (dirty filters or blocked coils). Turn off the AC and call a licensed technician.

How much does it cost to run an air conditioner?

A 2.5kW system costs about $0.30–$0.50 per hour. A 5kW system costs about $0.60–$1.00 per hour. Inverter systems save 30–50% on running costs. Read our full guide on split system running costs in Brisbane.

Do you provide a warranty on repairs?

Yes. All our repair work comes with a workmanship warranty. Parts come with a manufacturer’s warranty.

How quickly can you come out?

Most AC repairs can be done same-day or next-day. Call us in the morning, and we’ll usually have it sorted by the afternoon.

Aaron Ross is a licensed electrician and owner of Amplus Electrical & Air in Capalaba, Brisbane. He holds Queensland Electrical Contractor Licence #1500996 and ARCtick Licence AU number for refrigerant handling. Amplus serves Brisbane, the Redlands, and Bayside suburbs with same-day air conditioning installation and repair.

Need a Licensed Electrician in Brisbane Bayside?

Aaron is a licensed electrician (Lic. 1500996) and ARC-certified A/C technician serving Capalaba, Cleveland, Wynnum, Manly, Birkdale, Thornlands, Victoria Point and surrounding suburbs. Honest advice, upfront pricing, and quality work guaranteed.

Aaron Ross — Licensed Electrician Brisbane

About Aaron Ross

Licensed Electrical Contractor & Air Conditioning Specialist

Aaron is the founder of Amplus Electrical & Air, a family-owned business serving Brisbane's Redlands and greater Brisbane area. With over 15 years of hands-on experience, Aaron specializes in residential electrical work, smoke alarm compliance, EV charger installations, and air conditioning systems.

  • QLD Electrical Contractor Licence: #1500996
  • ARCtick: Refrigerant Handling Licence
  • Service Area: Brisbane, Redlands, Capalaba & surrounds
  • Phone: 0419 014 146
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