Q: Does Running My AC in the Summer Keep My Engine Cooler?

Automotive air conditioning (AC) will cause the engine to run hotter in the summer because it creates more heat in the engine compartment and there will be more strain on the engine to operate the AC compressor. The AC compressor works with a clutch - kind of like a standard transmission - but it is magnetic and is regulated with different high and low pressure sensors that cause it to cycle off and on. Every time it cycles on it creates more strain on the engine and in turn will create heat. If the AC cycles on and off continuously, you have issues with either low refrigerant levels or something else wrong in the system. The engine’s serpentine belt drives the AC compressor, which requires more energy from the engine. You may actually notice a slight decrease in performance and fuel economy when the air conditioning is engaged.

When the AC is running, you’ll likely hear the engine fan running louder if you do not have electric fans. Either the fan operates at a higher speed to combat the extra engine heat generated, or there may be a secondary electric air conditioning fan that runs when the AC is turned on to provide extra cooling. It is turned on by the cooling fan module or a body control computer that will command the relay to operate.

If you notice the engine temperature climbing higher than normal when the air conditioning is off, it can be a sign of a problem with the cooling system. If the engine runs hotter than normal with the AC turned on, there could be an issue with the AC electric cooling fan. If you have issues with the vehicle overheating in the city but not on the highway, this is a fan issue, meaning the fans are not operating. You actually could turn the AC on to help cool down the engine if the electric engine fan is not working. However, in order for this to work your vehicle would have to be equipped with two electronic cooling fans. You should have your vehicle checked by an experienced technician.