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If your car is working properly, turning on the air conditioning (A/C) should not cause the engine to overheat. The engine and cooling system are designed to handle the additional stress created by the A/C system under normal conditions.

Problems only occur when there’s an underlying issue with the cooling system or (in some rare cases) the A/C compressor, as we’ll discuss below.

Why Does My Car Overheat When the A/C is on?

When you switch on your car’s A/C, the A/C compressor turns on to push refrigerant through the system. Because the compressor is driven off the engine by a belt, it puts an additional load on the engine. Also, the temperature of the A/C condenser, which sits right in front of the engine’s radiator, increases when the A/C is turned on.

Replacement AC Compressor Isolated
When you switch on your car’s A/C, the A/C compressor turns on to push refrigerant through the system.

Under normal circumstances, the demands imposed by the A/C system will not cause the engine to overheat because fan(s) automatically turn on to keep things cool. However, if the cooling system is already having problems, engaging the A/C may push the engine to the point of overheating.

Common cooling system problems that can lead to overheating when the A/C is turned on include:

Also, although somewhat rare, a bad A/C compressor that’s difficult to turn can put an additional strain on the engine, potentially resulting in overheating.

Overloading the car is another possibility. For example, if you’re towing a trailer that’s well beyond the vehicle’s rated capacity, overheating may result when the A/C is turned on.

Related FAQ

Does A/C Make the Engine Hotter?

Under normal operating conditions, turning on the A/C system will not make the engine run hotter. When the A/C is activated, one or more cooling fans turn on automatically to provide additional airflow and keep things cool.

Should You Turn on the A/C if Your Car is Overheating?

No, you definitely should not turn on your car’s A/C if the engine is overheating. The best plan is to pull over, turn the engine off immediately, and arrange for a tow truck. Allowing your car to overheat even once can cause extensive engine damage.

If you must continue driving for whatever reason, turn the A/C OFF and the heater ON. Turning on the heater will draw excess heat through the heater core (a type of radiator), causing the engine coolant’s temperature to drop slightly.

Keep in mind, however, that the engine can still overheat with the heater on, so you’ll need to monitor the temperature gauge carefully. Also, the heater trick usually won’t work if the system is low on coolant since there isn’t enough flow through the heater core.

What Should I Do If My Car Runs Hot When the A/C is On?

There’s something wrong with your car if the engine is overheating when the A/C is switched on. You (or your mechanic) will need to do some diagnostic work to determine the root cause of the problem.

Once again, allowing your car to overheat even once can cause internal engine damage, so you’ll want to address the overheating issue immediately.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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