Why Does My Car Overheat When the AC Is On?

Driving comfortably in the AC, unfazed and indifferent to the outside simmering heat, when you suddenly notice the engine light going all red.

It’s blinking red hot!

You stop the car, shut the engine and wait for it to cool off.

This has now become a routine, and a major source of inconvenience for you. It’s getting into your nerves.

Every time you turn on your car’s AC, few minutes and miles later, your car’s temperature overshoots.

So why is this happening? Why does your car overheat whenever you turn the AC on?


Engine overheating with AC on is generally caused by one of two possibilities: overloading and inefficient working of the cooling system.

Let’s look into the details of each.

Your car’s AC unit has a compressor, just like the AC unit at your home. It’s the compressor that does all the work and keep your car’s environment cool and pleasant when Mother Nature is unforgivingly hot.

With time, your car’s AC compressor develops wear and tear; it ages. An ageing compressor loses efficiency and becomes a little lazy. Your car’s engine which is responsible for keeping the compressor in working order, now has to put in extra effort to make the old compressor work. This increases load on your car’s engine and as a result it overheats.

Similarly, your car’s engine may also overheat if your car’s cooling system is not working efficiently.