Why is my car's air conditioning blowing warm air?

The most common cause is low refrigerant — the gas the system relies on slowly leaks out over the years, so the air gradually gets less cold until it's just blowing warm. Other causes include a refrigerant leak, a failed compressor, a blocked condenser, or an electrical or sensor fault. A diagnostic check pinpoints which.

What is an air con regas and how much does it cost?

A regas removes the old refrigerant and refills the system to the correct level, usually with a check for leaks. As a rough guide it costs somewhere in the region of £50–£90 for older systems and more for newer cars that use the pricier R1234yf refrigerant. Prices vary by garage and gas type, so it's worth comparing.

How often should I regas my car's air conditioning?

Many manufacturers suggest a regas every 2–3 years, as systems naturally lose a small amount of refrigerant over time even with no fault. If your air con has gradually become less cold, it's usually due. Running the air con briefly all year round — even in winter — also helps keep the seals healthy.

Why does a regas not fix my air con?

If the system has an actual leak, a failed compressor or a blocked condenser, simply adding gas won't fix it — the gas will leak straight back out or the system won't circulate it. That's why a good garage checks for leaks and faults first, rather than just topping it up.

Is air conditioning checked in the MOT?

No. Air conditioning is not part of the MOT test, so a faulty system won't cause a fail — but it also means no one flags it for you. It's worth getting it looked at separately if it's not performing, especially before summer.

Car Air Con Not Cold? Causes, Fixes and What a Regas Costs

There's nothing like turning on the air con on a hot day and getting a face full of warm air. If your car's air conditioning has lost its cool, here's what's likely behind it, what each fix costs, and how to keep it working.

Why it's blowing warm

The single most common reason is simple: low refrigerant. Car air con relies on a sealed gas that, over the years, slowly seeps out — so the air gets gradually less cold until one summer it's just warm. It's not necessarily a fault; it's normal ageing of the system.

But there are other culprits worth ruling out:

A refrigerant leak — a faulty seal, hose or component letting the gas escape faster
A failed compressor — the pump that circulates the gas; an expensive part
A blocked or damaged condenser — often from road debris
An electrical or sensor fault — stopping the system running properly

A diagnostic check tells you which of these you're dealing with before you spend money.

What a regas costs

A regas removes the old refrigerant and refills the system to the right level, usually with a leak check. As a rough guide:

Older systems (using R134a gas): around £50–£90
Newer cars (using the pricier R1234yf gas, broadly 2017-onwards): noticeably more

Prices vary a fair bit by garage and gas type, so it's worth getting a couple of quotes rather than taking the first. If your air con has just gradually gone weak with no other symptoms, a regas often restores it completely.

When a regas won't fix it

Here's the catch: if there's an actual leak, a failed compressor or a blockage, adding gas won't help — it'll either leak straight back out or fail to circulate. That's why a decent garage checks for faults before topping up, rather than charging you for gas that vanishes in a week. If you've had a regas and the cold didn't last, you likely have a leak that needs finding and fixing.

Keeping it healthy

A few habits keep your air con working and head off bills:

Run it regularly — even in winter. Using the air con for ten minutes now and then keeps the seals lubricated and stops them drying out and leaking.
Use it to demist in cold, damp weather; it dries the air fast.
Regas every 2–3 years as a matter of routine, as recommended by many manufacturers.

Worth knowing: it's not an MOT item

Air conditioning isn't part of the MOT, so a weak system won't fail your test — but it also means nobody flags it for you. If it's not performing, treat it as a separate job and get it looked at, ideally before the summer heat arrives rather than during it. While you're booking a garage, you can also check your car's MOT history and what's due free with the registration, and line up any other work in one visit.

The bottom line

Warm air con is usually just low refrigerant — a regas in the £50–£90 region often sorts it. But if a top-up doesn't last, you've got a leak or a failed part that needs proper diagnosis. Keep the system used year-round, regas every couple of years, and don't wait until the first heatwave to discover it's not working.