What Should I Check Before Calling an Air Conditioning Technician?
Introduction
Why Bother Checking First? (The Case for a Quick DIY Look)
When an air conditioner stops working, the instinct is to call a technician straight away. But many of the most common faults have simple causes that you can confirm, and often fix, in under 10 minutes. Knowing what to check before calling an air conditioning technician means you're not paying for a callout when the problem is a tripped breaker or a remote set to fan mode.
This guide walks you through seven practical checks, starting with the simplest and working toward the more involved. Each check focuses on a specific part of the system: power supply, remote control, air filters, the outdoor unit, fault codes, water and smell indicators, and a system reset. Work through them in order before picking up the phone.
Some faults genuinely do need a licensed technician, and this guide will be direct about where that line is. But understanding why is my air conditioner not working, and how far you can safely go in diagnosing it yourself, saves time and money every time.
Section 01
Check 1: Is the Power Actually On?
This is the most common cause of an air conditioner appearing dead. Power issues account for a surprisingly large share of no-fault callouts, so always confirm power first.
Check each of the following before moving on:
Circuit breaker: Go to your switchboard and look for the breaker labelled "air conditioning" or "AC". If it's tripped (sitting in the middle position), flip it fully off and then back on. A breaker that trips again immediately signals an electrical fault. Stop here and call a technician.
Isolator switch: Most split systems have a dedicated isolator, a small box on the external wall near the outdoor unit. Check that it's switched to the on position.
Power board or GPO: If the indoor unit plugs into a power board or a General Purpose Outlet (GPO), check that the outlet or board is switched on and hasn't tripped its safety switch.
Active power outage: Check whether other appliances in your home are working normally. If there's a street-level outage, your air conditioner isn't faulty at all.
If power checks out on all fronts and the unit still won't respond, move to Check 2.
Section 02
Check 2: Is the Remote Control Set Correctly?
A remote control issue is one of the most overlooked causes of an air conditioner that seems to be working but isn't cooling. The unit might be running in fan-only mode, heating mode, or set to a temperature warmer than the room.
Check all of the following on your remote:
Mode: Make sure the unit is set to COOL (snowflake symbol), not FAN, DRY, or HEAT.
Set temperature: The target temperature must be lower than the current room temperature for the system to cool. Set it to at least 3 to 4 degrees below the room temperature.
Fan speed: If fan speed is set to the lowest setting, airflow may feel insufficient even when the unit is working perfectly. Try increasing it.
Timer or schedule: Check whether a timer has been set that's keeping the unit off during certain hours.
Child lock: Some remotes have a lock feature that disables buttons. Check your manual to see if this is active.
Is Your Remote's Battery Dead?
A remote with a dying battery sends a weak or inconsistent signal. The unit may appear to receive the command (you hear a beep) but doesn't actually register the input correctly. Replace the batteries with fresh ones and try again. If the unit responds to the manual buttons on the indoor head but not the remote, the remote is the problem, not the air conditioner.
Section 03
Check 3: When Did You Last Clean the Filters?
Can a dirty air conditioner filter cause it not to work? Yes, absolutely. A blocked filter is one of the most common reasons an air conditioner stops cooling effectively, and it can even cause the system to shut itself down entirely.
Filters are designed to catch dust, pet hair, and airborne particles before they reach the evaporator coil (the cooling component inside the indoor unit). When filters are blocked, airflow drops sharply. The evaporator coil gets too cold without enough warm air passing over it, and it freezes. Once frozen, you'll notice the unit running but not cooling, dripping water, or shutting off automatically.
Manufacturers generally recommend cleaning filters every 2 to 4 weeks during periods of heavy use. If you haven't done it recently, this could be your entire problem.
Here's how to clean them safely:
Turn the unit off at the remote and wait for the fan to stop completely.
Open the front panel of the indoor unit. It usually clips up or swings open without tools.
Slide the filter panels out carefully. They slide forward and down.
Take them outside and shake off loose dust, then rinse them under cool running water.
Allow them to dry fully in the shade. Never in direct sunlight, as this can warp the plastic mesh.
Refit the dry filters and close the panel before turning the unit back on.
If the coil behind the filters looks coated in thick grey dust or you can see ice on it, leave the unit off for 30 to 60 minutes to allow it to thaw before restarting. For a blocked or dirty coil, you'll want a professional air conditioning service in Sydney, not just a filter clean.
Section 04
Check 4: Is the Outdoor Unit Blocked or Running?
If your air conditioner is working but not cooling the house, the outdoor unit is often the reason. The outdoor unit (also called the condenser) has one job: to push the heat it collects from inside your home out into the external air. If that process is blocked, the whole system overloads.
Go outside and look at your outdoor unit. Check for each of the following:
The fan is spinning: Stand close enough to see through the top grille. You should be able to see or hear the fan turning. If the compressor hum is there but the fan isn't spinning, the fan motor has likely failed.
Blocked airflow: Leaves, garden waste, overgrown bushes, or plastic bags caught in the grilles restrict airflow dramatically. Clear any debris from around and on top of the unit.
Minimum clearance: Split system outdoor units need at least 30 cm of clearance on the side where air exits. Ducted outdoor units typically need more. Check your unit isn't buried against a wall or fence.
Coil condition: Look through the side grilles at the fins (the thin metal rows around the outside). If they're matted with grass clippings, pet fur, or heavy dust, airflow is compromised. This requires a professional clean with correct tools.
Ice on the unit: Ice forming on the outdoor unit in warm weather usually means the refrigerant level is low or there's a blockage in the refrigerant circuit. Call a technician.
If the outdoor unit looks clear and the fan is spinning normally, that's not the issue. Move to Check 5.
Section 05
Check 5: Is There an Error Code Showing on the Display?
Modern air conditioning systems are designed to self-diagnose. If something goes wrong, most units display an error code on the indoor unit's LED display or through a flashing pattern on the indicator lights.
If you see a code, don't ignore it. It's the system telling you exactly what's wrong.
Take a clear photo of the display showing the full code.
Note your air conditioner brand and the indoor unit model number (usually printed on a label inside the front panel or on the right side of the unit).
Check your owner's manual. Most manuals include a fault code list in the back. Daikin, Mitsubishi Electric, and Fujitsu all publish these online too.
Cross-reference the code. Some codes, like a filter service reminder, you can clear yourself by cleaning the filter and resetting the counter from the remote.
If the code references refrigerant, the compressor, the inverter board, or a temperature sensor fault, stop here. These require a licensed technician. Don't attempt to clear them yourself by cutting the power repeatedly.
Having the error code ready when you call is one of the most useful things you can do. It allows the technician to arrive with the right parts, which often means the job is done in a single visit.
Pro tip from our team
For any air conditioner repair in Sydney, give us the fault code when you call and we can often provide a preliminary diagnosis over the phone before we even book the job.
Section 06
Check 6: Have You Noticed Any Water Leaks or Unusual Smells?
Water dripping from your indoor unit is one of the most common issues homeowners notice. A small amount of condensation around the unit in humid weather is normal. A steady drip or a water stain growing on your ceiling is not.
The most likely cause of an indoor water leak is a blocked condensate drain line. The drain carries condensation away from the evaporator coil. When it blocks, usually with mould, algae, or debris, water backs up and overflows into the unit. Clearing a drain line requires a technician with the right equipment. It's not a safe DIY job.
Other water leak causes include the following:
A frozen evaporator coil thawing, usually caused by a blocked filter (see Check 3).
A low refrigerant charge causing coil temperatures to drop below freezing.
The indoor unit being installed slightly off-level, causing water to pool and overflow.
Different odours mean different things:
Musty or mouldy smell: Mould or bacteria has built up in the filters, coil, or drain pan. A professional clean will fix this.
Dusty or slightly burnt smell on first use: This is normal at the start of a new season when dust burns off the coil. It should clear within a few minutes.
Persistent burning or electrical smell: Stop the unit immediately. This signals an electrical fault inside the system. Do not restart it. Call a technician the same day.
Rotten egg or chemical smell: Could indicate a refrigerant leak. If the smell is strong, ventilate the area and call a technician.
Section 07
Check 7: Try a Safe System Reset
If you've worked through checks 1 through 6 and everything looks fine but the system still isn't running normally, try a full system reset. This clears minor fault memory stored in the unit's control board and allows the system to restart from a clean state.
Here's how to do it correctly:
Turn the air conditioner off using the remote control or the manual button on the indoor unit.
Switch the unit off at the wall isolator (the switch on the external wall near the outdoor unit) or at the circuit breaker in your switchboard.
Wait a full 5 minutes. This gives the capacitors inside the system time to discharge and the control board to fully reset. A shorter wait may not clear the fault memory.
Restore power at the isolator or breaker first.
Wait another 60 seconds before turning the unit on with the remote. The system needs a moment to reinitialise its components.
Set the unit to cooling mode, set a temperature 3 to 4 degrees below the current room temperature, and monitor it for 15 minutes.
If the unit starts, runs, and begins cooling the room normally, you've fixed it. If the same error code returns, the unit shuts down again, or it still won't cool, you're at the point where a technician is required.
Safety first: Do not reset if you notice any of these
A burning or electrical smell from the unit.
Visible sparks or scorch marks near the unit.
Water dripping near any electrical components or wiring.
A circuit breaker that trips again immediately after you reset it.
Check your outdoor unit for blocked airflow, debris, and whether the fan is running. A common step in any air conditioner check before service in Sydney.
Safety Escalation Module
When to Stop Checking and Call a Technician
The 7 checks above cover the vast majority of common faults. But there are situations where stopping and calling a professional isn't just the smarter choice. It's the only safe one.
Call for air conditioning repair in Sydney immediately if any of the following apply:
The circuit breaker keeps tripping every time you reset it.
You can smell burning or see any sign of electrical damage.
There's water dripping near wiring or an electrical panel.
The outdoor unit is making a loud banging, grinding, or screeching noise.
The indoor unit is producing ice or frost on the vents during operation.
The unit runs constantly but the room temperature never drops.
You see yellowish oily stains near the refrigerant pipe connections. This is refrigerant oil and indicates a leak.
Things You Should Never Attempt Yourself
Under Australian law, certain air conditioning work is strictly regulated and requires a licensed technician. The following are not DIY tasks:
Refrigerant handling: Adding, removing, or recovering refrigerant requires an ARC (Australian Refrigeration Council) licence. It's illegal to handle refrigerant without one.
Internal electrical repairs: Replacing capacitors, contactors, inverter boards, or any wiring inside the unit requires a licensed electrician or refrigeration mechanic.
Coil cleaning with chemicals: Incorrect chemicals damage aluminium fins permanently. Coil cleaning should use the right products at the right dilution.
Dismantling the outdoor unit: The compressor stores high-pressure refrigerant and operates at dangerous voltages. Opening the outdoor unit casing without training and tools is genuinely dangerous.
Saying you can't safely do this yourself isn't a scare tactic. It's the honest truth, and trusting a licensed technician for these tasks protects both you and your warranty.
Preparing for Your Service Call
What to Tell the Technician When You Call
The more information you give the technician upfront, the faster and cheaper your repair is likely to be. Here's exactly what to have ready when you call for air conditioner repair in Sydney:
Information to have ready before you call
Brand & Model
For example, Daikin FTXF25WVMA or Mitsubishi MSZ-AP25VG. Found on the label inside the front panel of the indoor unit.
Error Code
The exact code shown on the display or a photo of the flashing indicator light pattern.
What It's Doing
Be specific. "It powers on, fan runs, but no cold air" is far more useful than "it's not working".
How Long
How long has the problem been happening? Did it start suddenly or gradually worsen over days?
Recent Changes
Have you had any power outages, storms, or unusual events before the fault started?
Checks You've Done
Tell them you've already checked the power, filters, outdoor unit, and done a system reset. This saves diagnostic time.
Last Service Date
When was the system last serviced or cleaned? This gives the technician context on the likely condition of the coils and drain.
At Skycon Air, we're an authorised dealer for Daikin and Mitsubishi Electric, which means our technicians are factory-trained on the units they're repairing. That's not just a credential. It means less guesswork and faster results on your job.
Frequently Asked Questions
1
What is the first thing I should check when my air conditioner stops working?
Start with the power. Check that the circuit breaker for the air conditioner hasn't tripped, that the isolator switch on the wall near the outdoor unit is in the on position, and that the indoor unit is actually receiving power. Many no-start calls turn out to be a tripped breaker or a power board that's switched off. If power is confirmed on all fronts and the unit is still unresponsive, move on to checking the remote control settings and battery.
2
Can a dirty filter cause my air conditioner to stop working completely?
Yes, it can. A severely blocked filter restricts airflow to the point where the indoor evaporator coil freezes over. Once frozen, the unit either stops producing cool air entirely or shuts itself down on a safety timer. Cleaning the filter and allowing the coil to thaw for 30 to 60 minutes often restores normal operation. This is why manufacturers recommend cleaning filters every 2 to 4 weeks during heavy use periods.
3
Is it safe to reset my air conditioner myself?
Yes, a basic reset is safe for most homeowners. Turn the unit off at the remote or wall controller, switch it off at the isolator or circuit breaker, wait a full 5 minutes, then restore power and turn the unit on again. This clears most minor faults stored in the control board. Do not attempt a reset if you can smell burning, if the breaker trips again immediately, or if there's water near any electrical component.
4
Why is my air conditioner running but not cooling the house?
The most common causes are a clogged filter reducing airflow, a blocked outdoor unit preventing heat rejection, the system being set to fan-only mode instead of cooling, or low refrigerant from a slow leak. Check the filter and outdoor unit first, then confirm the remote is set to cooling mode at a temperature below the room temperature. If those checks all pass, you most likely have a refrigerant or compressor issue that needs a licensed technician.
5
What does it mean when my air conditioner shows an error code?
Error codes are fault signals the system displays when it detects a problem it can't self-correct. Each code maps to a specific fault. Brands like Daikin, Mitsubishi Electric, and Fujitsu publish full error code lists in their owner's manuals and on their websites. Take a photo of the code, note your brand and model number, then look it up. Codes referencing refrigerant pressure, compressor faults, or temperature sensor failures need a licensed technician.
6
When should I not try to fix my air conditioner myself?
Stop immediately and call a technician if you smell burning or see electrical scorch marks, if there are sparks from the unit, if water is dripping near any wiring or electrical component, if you hear a loud bang or grinding noise from the outdoor unit, or if you notice yellowish oily stains near the refrigerant pipe connections. Under Australian law, refrigerant handling and internal electrical repairs on air conditioning systems require a licensed technician.
7
How much does it cost to call an air conditioning technician in Sydney?
In Sydney, a standard callout and diagnostic fee typically ranges from $80 to $150, with the cost of the repair added on top once the fault is found. Simple repairs such as clearing a drain blockage, replacing a capacitor, or topping up refrigerant can range from $150 to $400. At Skycon Air, we provide a clear, upfront quote before any work begins, so there are no surprises on the final bill.
Conclusion
Still Stuck? Here's What Matters Most
Running through these 7 checks before calling a technician takes under 10 minutes and resolves the problem in a good portion of cases. Start with power, check the remote, clean the filters, inspect the outdoor unit, note any error code, look for leaks or smells, and try a full system reset.
If you've done all 7 checks and the system is still not running correctly, or if you hit any of the safety red flags along the way, that's when you call a professional. An experienced technician doing a proper air conditioner check before service in Sydney will pinpoint the fault quickly, quote you upfront, and fix it right the first time.
At Skycon Air, we service all major brands including Daikin, Mitsubishi Electric, Fujitsu, Samsung, Hisense, and Rinnai. With a 4.9-star Google rating from over 240 Sydney customers and a team of fully licensed technicians for air conditioning in Sydney, we're ready to help when your checks don't solve it.
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Skycon Air is an authorised Daikin and Mitsubishi Electric dealer with a 4.9-star Google rating from 240+ Sydney reviews. We service all major brands and all system types, across the entire Sydney metro area.
