What to Do If Your Air Conditioning Breaks Down in a Heatwave

Sep 29

8 min read

If your air conditioning stops working in a heatwave, switch it off to prevent further damage, then check the thermostat, the fuse board, and the filter. Close blinds and windows to hold the cool air in and stay hydrated while you wait. If it still won't cool after these checks, call a certified engineer for emergency air conditioning repair.

A heatwave is the worst possible time for your air conditioning to fail and, unfortunately, the time it's most likely to. As temperatures climb, systems that have coped quietly all year are suddenly asked to work harder than ever, and even a small fault can tip them over the edge.

The reassuring news is that not every breakdown needs an engineer. Some of the most common causes are things you can safely check yourself in a few minutes. Below, we walk you through exactly what to do, how to stay comfortable while you wait, and when it's time to call us.

What should I do first when my air conditioning stops working in hot weather?

Work through these steps in order. They take only a few minutes and often get a unit cooling again without a call-out.

Switch the unit off: If your system is blowing warm air, making unusual noises, or leaking, turn it off at the remote and, where possible, at the wall. Forcing a struggling unit to keep running is the quickest way to turn a minor fault into an expensive one.
Check the thermostat: It sounds obvious, but settings get knocked. Make sure it's set to "cool" rather than "fan" or "heat", and that the target temperature is a few degrees below the current room temperature. Fresh batteries in the remote or wall controller are worth a try too.
Check your fuse board: Air conditioning draws a lot of power in hot weather, and a spike can trip a breaker. Find your consumer unit and look for a switch that has flipped off. Reset it once. If it trips again straight away, stop, leave it off, and call us — repeated tripping points to an electrical fault that needs an engineer.
Check and clean the filter: A blocked filter is one of the most common reasons a unit stops cooling properly. Remove the filter from the indoor unit; if it's grey with dust, rinse it under warm water, let it dry fully, and refit it. Clean filters restore airflow and can make a dramatic difference.
Clear the outdoor unit: The outdoor condenser needs space to breathe. Clear away leaves, grass cuttings, and anything stacked against it, and gently brush off the fins. A blocked outdoor unit can't release heat, so the whole system struggles.
Close blinds, curtains, and windows: Once you've checked, trap whatever cool air you have. Closing sun-facing blinds and windows stops hot air pouring in and gives your system or a fan a fighting chance.
Try Powerful mode: If your unit has a Powerful mode, switch it on and let it run for a few minutes. If it runs and cools properly in this mode, note it when you call us, as it helps our engineers narrow down the cause.

If your unit still isn't cooling properly after these steps, it's likely a fault, and a routine service won't fix it. A service is planned maintenance that keeps a healthy system running well; a fault needs a repair investigation, where our engineers diagnose what's gone wrong. Call us to book an investigation, and review the warning signs below so you can tell us what you've noticed. If the checks did solve it, for example, a tripped breaker or a dirty filter, booking a service ahead of next summer will help prevent a repeat.

How can I stay cool while I wait for a repair?

If your unit needs a repair, you can still keep your home and family comfortable. UK health guidance offers simple, effective ways to manage indoor heat.

Keep the sun out by day: Close blinds and curtains on windows that face the sun. UK Health Security Agency advice is to keep these closed during the day and open windows at night, when the air outside is cooler, to get air flowing through your home.
Use fans sensibly: Electric fans help when the air temperature is below 35°C, but government guidance advises against aiming a fan directly at your body, as this can increase dehydration. Instead, position it to move air around the room.
Stay hydrated: Drink water regularly throughout the day, not only when you feel thirsty, and limit alcohol and caffeine. A cool shower or a damp cloth on the back of your neck can cool you down faster than a fan.
Retreat to the coolest room: Move to the shadiest, coolest part of the house, often a north-facing or ground-floor room, especially for sleeping.
Reduce indoor heat: Turn off lights, ovens, and electrical equipment you aren't using, as they all add warmth to the room.

Keep a closer eye on older relatives, young children, and anyone with a heart or breathing condition, as they feel the effects of heat sooner.

How do I know if it needs an engineer, not a DIY fix?

If you've worked through the checks above and your system still isn't cooling, the fault is likely beyond a DIY fix. Certain warning signs mean you should stop using the unit and call a professional rather than risk further damage.

Call an engineer if you notice any of the following:

No cold air despite all your checks: the thermostat, filter, and breaker are fine, but the air still won't cool.
Warm air only: often a sign of low refrigerant or a compressor problem.
Ice on the unit or pipework: usually caused by low refrigerant or restricted airflow, and a clear signal to switch off.
Water leaking from the indoor unit: a blocked drain or another fault that can damage your home if ignored.
A breaker that keeps tripping: a serious electrical warning sign; leave the unit off.
Unusual noises: grinding, rattling, or buzzing points to a mechanical or electrical fault.

Here's a quick guide to what these symptoms usually mean and what to do:

Symptom	What it often means	What to do
Warm air only	Low refrigerant or compressor fault	Switch off, call an engineer
Ice on unit or pipes	Low refrigerant or restricted airflow	Switch off, let it defrost, call us
Water leaking indoors	Blocked condensate drain or fault	Switch off, call us
Breaker keeps tripping	Electrical fault	Leave off, call us immediately
Grinding or rattling noises	Mechanical or fan fault	Switch off, call an engineer
No cold air after all checks	Multiple possible causes	Book a repair

Refrigerant work is not a DIY job; by law, a qualified, refrigerant-certified engineer must handle it. Our certified team repairs refrigerant leaks, faulty compressors and fan motors, thermostat faults, and electrical issues across all major brands, for both domestic and commercial systems.

Why does air conditioning break down in a heatwave?

It's no coincidence that breakdowns spike when the weather does. A heatwave puts your system under sustained strain in three ways.

It runs harder, for longer: In mild weather, your unit cools in short bursts. In a heatwave, it can run for hours without a break, and components that were just about coping reach their limit.
Small faults get exposed: A slightly low refrigerant level, a tired compressor, or a partly clogged filter may go unnoticed all winter. Under peak load, these minor issues can cause your system to fail.
Demand is at its highest: Everyone needs cooling at once, which is exactly when a fault is least convenient.

That is why we always recommend servicing before summer rather than during it. An annual air conditioning service checks refrigerant levels, cleans filters and coils, and catches the small problems that cause mid-heatwave breakdowns. Our guide on whether you should service your air con explains what's involved and why it pays off, and a warranty or care plan can keep your system protected and running efficiently year after year.

When should I call for emergency air conditioning help?

If your system won't cool after the checks above, or you've spotted any of the warning signs, don't wait for the fault to get worse. We provide emergency and planned air conditioning repairs for homes and businesses across Leicester and the surrounding areas, with rapid response and certified engineers who work on all major brands.

Call us as early as you can. Demand is high during a heatwave, so contacting us quickly gives you the best chance of an early visit. When you call, tell us the make of your unit, what it's doing (or not doing), and any warning signs you've noticed so we can arrive prepared.

Whether it's a home unit that's stopped cooling or a commercial system keeping your business running, we're here to get you comfortable again. Get in touch or call us on 0116 4030540 to book your repair.

Your heatwave AC breakdown checklist

Switch it off first if it's blowing warm, leaking, or making odd noises. Don't force a failing unit to run.
Do the five-minute checks: thermostat, fuse board, filter, and outdoor unit.
Hold the cool: close sun-facing blinds and windows; open up at night.
Stay safe in the heat: hydrate, use fans below 35°C, and keep to the coolest room.
Call an engineer for warm-air-only, ice, leaks, repeated tripping, or unusual noises.
Prevention beats repair: an annual service before summer stops most heatwave breakdowns.

Book your emergency air conditioning repair in Leicester

For expert air conditioning installation, servicing, and repairs across Leicester and the surrounding areas, contact Leicester Air Conditioning Services Ltd today. Our showroom is at 8 Hannah Parade, Stonehill Ave, Birstall, Leicester, LE4 4JE, and our registered office is at 51 Verdale Avenue, Leicester, England, LE4 9TH. Call us on 0116 4030540. With 150+ five-star reviews, our certified engineers are trusted throughout Leicester, Nottingham, Derby, and beyond for reliable, energy-efficient solutions.

Frequently asked questions

Do you provide emergency air conditioning repair services?

Yes. We offer emergency air conditioning repairs to address urgent breakdowns promptly across Leicester and the surrounding areas. Whether your system has stopped cooling in a heatwave or failed at your business, our certified engineers handle emergency and planned repairs on all major brands, including central units, split systems, and heat pumps. Call us to get booked in.

How quickly can you respond to a repair?

Response times depend on demand, your location, and the fault, and we're naturally busier during a heatwave. We prioritise urgent breakdowns and aim to attend as quickly as possible. The fastest way to get help is to call us directly on 0116 4030540 so we can assess the issue and arrange the earliest available visit.

What are the most common air conditioning problems?

The problems we see most often are refrigerant leaks, clogged or dirty filters, thermostat faults, blocked airflow, faulty compressors or fan motors, and electrical issues that trip the breaker. Many start small and worsen when the system runs hard in hot weather. Regular maintenance catches most of them before they cause a breakdown.

What should I do when my air conditioning stops working in hot weather?

First, switch the unit off to prevent further damage. Check the thermostat settings and your fuse board for a tripped breaker, then inspect the filter and clear any debris around the outdoor unit. Close blinds and windows to hold the cool air in. If it still won't cool, contact us for a repair.

Why does air conditioning fail in a heatwave?

Heatwaves push systems to run harder and longer, exposing existing weaknesses such as low refrigerant, a tired compressor, or clogged filters. Higher demand means more strain, so minor faults that went unnoticed in mild weather suddenly cause a system failure. A pre-summer service is the best way to reduce the risk.

How can I keep my house cool without air conditioning?

Keep blinds and curtains closed on sun-facing windows during the day, and open windows at night when it's cooler to get air flowing. Use fans if the temperature is below 35°C, stay hydrated, and move to the coolest room. A damp cloth on the back of your neck also helps you cool down quickly.

Is it safe to keep running a faulty air conditioning unit?

No. Running a faulty unit can turn a small, affordable fault into a major repair, and issues such as electrical faults, water leaks, or ice build-up can pose safety risks. If your system trips the breaker, leaks water, or makes unusual noises, switch it off and call an engineer instead of forcing it to keep running.