Why car air con needs a regas, and what the garage actually does

If your car's air conditioning is blowing warm or has stopped feeling as cold as it used to, it may need a regas. Here's why it happens, and what the garage actually does.

Why does air con need regassing?

Air conditioning works by circulating a refrigerant gas in a sealed system. In theory it never runs out, but in practice a small amount slowly escapes through the hoses and seals, even when nothing is broken. A commonly quoted figure is around 10% a year. Over a couple of years the system can be low enough that it stops cooling properly.

Many manufacturers suggest having the system checked and regassed roughly every two years. Some cars hold on to their gas for longer, and some leak faster.

Signs your air con needs attention

• The air from the vents is warm or only slightly cool.
• It takes much longer to cool the car than it used to.
• The cold air comes and goes.
• The system hasn't been looked at for around two years.

Weak airflow on its own isn't always a gas problem. A blocked cabin filter is a common cause, and it's a cheaper fix.

What a regas actually involves

A proper regas is a mini service, not a top-up from a can:

1. The old refrigerant is recovered from the system.
2. The system is put under a vacuum to remove air and moisture.
3. The garage checks whether the system holds the vacuum, which shows whether there's a leak.
4. The right amount of the correct refrigerant is put back, with lubricating oil if needed.
5. The system is run to check it cools properly.

The vacuum step matters because moisture in the system can cause corrosion and damage components. If the garage finds a leak, the regas won't last until the leak is repaired. A quick top-up that doesn't check for leaks is only a short-term fix.

What does it cost?

A regas typically costs about £50 to £150, depending on your car and the garage. If the system needs repairs, such as a leaking hose, condenser or compressor, the bill can reach £100 to £300 or more. Newer cars often use a more expensive refrigerant, so check the price with the garage before booking.

Keep it healthy

• Run the air con for a few minutes every few weeks, even in winter. It helps keep seals lubricated.
• Replace the cabin filter on schedule.
• Don't ignore a musty smell. A garage can clean the system.

Is it part of the MOT?

No. Air conditioning isn't tested in an MOT, so a car can pass with no working air con. It's worth asking for it to be checked at a service.