Should You Run Your Air Con in Winter?
Plenty of drivers think of air con as a summer luxury and leave the button alone from October to April. Then a damp morning arrives, the windscreen mists over from the inside, and the heater seems to make no difference.
Using the A/C button in cold weather sounds odd, but there are good practical reasons to do it. Here is how it works and what to keep in mind.
Why cooling helps you get warm and clear
Misted windows happen when moist air inside the car meets cold glass and condenses. The fix is to get rid of the moisture, and that is exactly what the air-con system does. As air passes over the cold evaporator, moisture condenses out of it and drains away, so the air that comes out is drier.
When you combine that with the heater, the air is dried first and then warmed to the temperature you want. The result is dry, warm air blowing at the glass, which clears condensation far faster than warm, humid air alone. That is why most cars switch the compressor on automatically when you select the demist setting.
- Select the demist setting and turn the temperature up.
- Press the A/C button if it has not engaged automatically.
- Turn recirculation off so fresh, drier air comes in.
- Direct the air to the windscreen and side windows.
Keeping the system in good order
The air-con compressor relies on refrigerant oil circulating through the system to keep its internal parts and the seals supple. If the system sits unused for months, seals can dry out and become more likely to weep. Running the air con regularly, even for a short time each week or fortnight, helps keep everything moving and lubricated.
It is not a cure for an ageing system, and there are no promises that regular use will stop a leak from ever developing. But a system that has been used steadily through the year tends to be in better shape when summer returns than one that has sat idle.
What about fuel use?
Running the compressor places an extra load on the engine, so in general terms it can increase fuel use a little. How much depends on the car, the conditions and how hard the system is working. In cold weather the compressor is doing less work than on a hot day, and the impact tends to be smaller.
For most drivers the trade-off is worthwhile when the alternative is poor visibility. Clear glass is a safety matter. If fuel economy is a concern, you can use the A/C only until the windows are clear and then switch it off, relying on the heater to maintain the temperature.
It also helps to keep the cabin filter in good condition and to avoid heavy use of the fan on its highest setting for no reason. Those small habits keep the system working efficiently, so you are not asking more of the engine than you need to.
Signs the system needs attention
Winter is a decent time to notice problems, because the demisting performance shows how the system is coping. If the windows take far longer than usual to clear, if there is a musty smell, or if the compressor makes a grinding or squealing noise when engaged, the system may need inspection.
Some cars will not run the compressor at all in very cold temperatures, as a protection measure, so the A/C may not engage when it is near or below freezing. That is normal behaviour and not necessarily a fault, though your handbook will tell you more about your own car.
A simple winter routine
A sensible routine is to use the A/C with the heater when you need to clear the windows, keep recirculation off in damp weather and run the system briefly each week even if you do not need it. Replace the cabin filter on schedule, because a clogged one hampers airflow and makes demisting harder.
If the system struggles, we can help. At Banks of the Tyne in Hebburn we offer air-con servicing, diagnostics and repairs, and heating-system repairs, so a winter check can look at both sides of the climate control.
Key takeaway: Pressing the A/C button in winter dries the air, clears misted glass faster and keeps the system moving. The effect on fuel use is generally modest, and safe visibility is worth it.
Frequently asked questions
Will using air con in winter damage my car?
No. Running it is normal and generally good for the system. Many cars engage the compressor automatically when you demist, so you may already be using it.
Why does my A/C button not work in very cold weather?
Some systems restrict compressor operation at low temperatures to protect themselves. If it also fails to work in mild weather, the system should be checked.
Should I use recirculation when it is cold?
Usually not in damp weather, as it traps moisture inside the car and increases misting. Fresh air mode with A/C on tends to clear the glass more effectively.
Need help with air conditioning & heating?
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Read the guide →Get a free quote
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