Why is my air conditioning not cooling the room?

If the fan runs but the air isn't cold, it's usually a dirty filter restricting airflow, low refrigerant from a slow leak, or the outdoor unit being blocked or struggling to dump heat. Clean the filter and check the outdoor unit isn't obstructed first — if it's still not cooling, refrigerant is sealed and needs an F-Gas engineer, not a DIY top-up.

Why is my air conditioning leaking water?

A leak almost always means the condensate drain is blocked rather than the unit itself failing. Check the drain pipe isn't kinked where it exits outside, and if a frozen coil has just thawed, that extra water can overwhelm the drain temporarily. A persistent leak needs the drain cleared professionally before it causes water damage.

Why is my air conditioning making a strange noise?

Buzzing usually means a loose panel or debris in the outdoor unit. Hissing can indicate a refrigerant leak. Grinding or screeching points to a failing fan motor or bearing — switch off and call an engineer rather than keep running it, since this can get more expensive if left.

Why won't my air conditioning turn on?

No response at all is usually electrical rather than refrigerant-related. Check for a tripped breaker at the consumer unit, confirm the isolator switch near the outdoor unit is on, and try fresh batteries in the remote. If power is confirmed present and it still won't start, the fault is internal and needs an engineer.

Why is there ice on my air conditioning unit?

A frozen coil is a symptom, not the problem itself — usually low refrigerant, restricted airflow from a dirty filter, or the thermostat set too low for the conditions. Switch to fan-only to let it thaw fully rather than chipping the ice off. If it ices up again within a day or two of normal use, that's a fault needing proper diagnosis.

Why does my air conditioning smell musty?

A musty smell is almost always mould or bacteria build-up on the evaporator coil or in the drain pan. Cleaning or replacing the filter helps, and running fan-only for ten minutes before switching off lets the coil dry out and discourages mould. A smell that persists despite a clean filter usually means the coil itself needs a professional clean.

Why is the outdoor unit of my air conditioning not running?

If the indoor unit has power but the outdoor unit stays silent, check the outdoor isolator switch first. Beyond that there's little to check safely yourself — a silent outdoor unit is commonly a failed capacitor, fan motor fault, or control board issue, and usually needs parts from an F-Gas engineer.

Should I repair or replace my air conditioning unit?

Replace if the unit is over 10-12 years old, still uses R22 refrigerant (which can no longer be legally topped up), needs repairs more than once a year, or running costs keep climbing despite servicing. Repair usually makes sense if it's under 8 years old, still under warranty, or this is its first fault.

How can I prevent my air conditioning from breaking down?

The single most effective prevention is an annual F-Gas service, ideally booked in spring before the first heatwave. Cleaning or replacing filters every one to three months in heavy use, and keeping the outdoor unit clear of debris and foliage, both significantly reduce the most common faults.

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Most Common Air Conditioning Problems — Wokingham Guide

Single-split, multi-split & commercial systems — symptoms, causes and fixes explained

Air conditioning faults across Wokingham and surrounding areas follow predictable patterns — most of them come down to a handful of repeat causes. Some can be sorted yourself in a few minutes; others are a clear sign to stop and call an F-Gas qualified engineer. This guide covers every common problem, what causes it, and exactly what to try first.

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Troubleshooting guide

7 common air conditioning problems — symptoms, causes & fixes

Most AC faults are one of a handful of repeat offenders — a dirty filter, a blocked drain, low refrigerant. Many can be sorted yourself in a few minutes; others are a clear sign to stop and call an F-Gas qualified engineer. Work through the one that matches what you're seeing.

Air conditioning not cooling the room

If the fan runs but the air isn't cold, it's almost always low refrigerant, a dirty filter restricting airflow, or the outdoor unit struggling to dump heat.

Symptoms

Fan runs but air isn't cold

Cooling is weak or inconsistent

Takes far longer than usual to cool the room

Common causes

Dirty or clogged filter restricting airflow

Low refrigerant — a sign of a leak, not something that's simply "used up"

Outdoor unit blocked, dirty, or starved of airflow

Try this first

Check and clean the filter — this alone fixes a large share of "not cooling" calls.

Check the outdoor unit isn't blocked by plants, debris or furniture.

Still not cooling? Refrigerant is sealed and needs an F-Gas engineer, not a DIY top-up.

Low refrigerant always means a leak somewhere. Book a diagnostic →

Air conditioning leaking water inside

A leak almost always means the condensate drain is blocked — not that the unit itself has failed.

Symptoms

Water dripping or pooling under the indoor unit

Damp patch on the wall below the unit

Water staining on the ceiling below a ducted or concealed unit

Common causes

Blocked condensate drain pipe (algae, dust, debris)

Condensate pump failure on units without gravity drainage

A frozen coil that's now thawing and overwhelming the drain

Try this first

Check the condensate pipe isn't kinked or blocked where it exits outside.

If the coil was iced up, run fan-only until it's fully thawed before cooling again.

Persistent leaks need the drain professionally cleared — don't ignore it, water damage gets expensive fast.

Water damage from a leak is far costlier than the fix. Book a repair →

Air conditioning making unusual noises

Buzzing, clicking or hissing each point to something different — a grinding or screeching noise means stop and call, not keep running it.

What the noise means

Buzzing or humming — loose panel or debris in the outdoor unit

Hissing — possible refrigerant leak

Grinding or screeching — failing fan motor or bearing

Symptoms

Noise from the outdoor unit, indoor unit, or both

A single click on start-up or shutdown is normal; repeated clicking isn't

Try this first

Check nothing's rattling loose on the outdoor unit casing.

Hissing or grinding noises: switch off and call an engineer rather than keep running it.

Book a diagnostic →

Air conditioning won't turn on

No response at all is usually electrical, not refrigerant — check the power path before assuming the worst.

Symptoms

No lights or display on the indoor unit

Remote gets no response

Outdoor unit completely silent

Common causes

Tripped RCD or breaker at the consumer unit

Isolator switch near the outdoor unit switched off

Remote control battery or sync issue

Try this first

Check your consumer unit for a tripped breaker.

Confirm the isolator switch (usually a grey box near the outdoor unit) is on.

Try fresh batteries and re-pair the remote. Still nothing? The fault is internal.

Book a repair →

Ice building up on the unit

A frozen coil is a symptom, not the problem itself — running it covered in ice makes whatever caused it worse.

Symptoms

Visible ice or frost on the indoor coil or outdoor unit

Reduced airflow

Unit running but barely cooling

Common causes

Low refrigerant

Restricted airflow from a dirty filter

Thermostat set too low for the conditions, or running continuously in high humidity

Try this first

Switch off and set to fan-only to let it thaw fully — don't chip the ice off.

Check and clean the filter once thawed.

Ices up again within a day or two? That's a refrigerant or airflow fault needing diagnosis.

Book a diagnostic →

Musty or unpleasant smell from the AC

A musty smell is almost always mould or bacteria build-up inside the unit — unpleasant, but straightforward to sort.

Symptoms

Musty, damp or stale smell when the unit runs

Smell fades after a few minutes, then returns next time

Common causes

Mould or bacteria growth on the evaporator coil or in the drain pan

Dirty filter trapping moisture

Condensate not draining properly, leaving standing water

Try this first

Clean or replace the filter.

Run fan-only for 10 minutes before switching off each time, to help the coil dry out.

Smell persists despite a clean filter? The coil itself likely needs a professional clean.

Book a service →

Outdoor unit not running

If the indoor unit powers on but the outdoor unit stays silent, the system can't actually cool — this needs an engineer, not a reset.

Symptoms

Indoor unit has power and display, but no sound from outside

Outdoor fan not spinning

Compressor silent

Common causes

Tripped isolator or breaker specific to the outdoor unit

Failed capacitor — a very common cause of a silent compressor

Fan motor failure or control board fault

Try this first

Check the outdoor isolator switch.

Beyond that, there's genuinely little to check safely yourself — this usually needs parts.

One of the more common F-Gas call-outs. Book a repair →

Beyond troubleshooting

Repair, replace, or prevent the next breakdown

Two questions that come up alongside almost every fault above: is this unit worth fixing, and how do you stop it happening again?

Should I repair or replace my air conditioning?

Signs it’s time to replace

Unit is over 10–12 years old

Still uses R22 refrigerant — no longer legal to top up

Requiring repairs more than once a year

Running costs climbing despite servicing

Signs repair is fine

Unit is under 8 years old

First or second fault in its lifetime

Still under manufacturer warranty

What to do

Book a diagnostic first — we’ll give you an honest repair vs replace recommendation.

A new A-rated inverter system typically cuts running costs significantly — see our sizing guide to get the right output for your room.

Book a diagnostic → · New system quotes →

How to prevent air conditioning breakdowns

Most common preventable faults

Frozen coils from a dirty filter restricting airflow

Leaks from a blocked condensate drain

Slow, undetected refrigerant leaks

Preventive actions

Annual F-Gas service — the single most effective prevention

Clean or replace filters every 1–3 months in heavy use

Keep the outdoor unit clear of debris and foliage

Book before summer

Book your annual service in spring, before the first heatwave hits and diaries fill up.

A service catches a slow refrigerant leak long before it becomes a no-cooling call-out.

Annual service from £96 →

Coverage

Air conditioning repairs across Wokingham & Berkshire

Based in Arborfield — 10 minutes from Wokingham town centre. Same-day where available across RG40 and RG41.

AC trouble? Call Stuart.

F-Gas Certified REF1025648 · £96 fixed diagnostic · 90% first-time fix · Same-day where available · Wokingham, Earley, Woodley & RG40

Book Online 24/7 07850 116944

Most Common Air Conditioning Problems — Wokingham Guide

7 common air conditioning problems — symptoms, causes & fixes

Air conditioning not cooling the room

Air conditioning leaking water inside

Air conditioning making unusual noises

Air conditioning won't turn on

Ice building up on the unit

Musty or unpleasant smell from the AC

Outdoor unit not running

Repair, replace, or prevent the next breakdown

Should I repair or replace my air conditioning?

How to prevent air conditioning breakdowns

Air conditioning repairs across Wokingham & Berkshire

More air conditioning & heating help

AC trouble? Call Stuart.