Don't turn on your air-conditioning when starting the car, fact or myth?

Which type of car owner are you? Are you the type who makes sure your car air-conditioning is off before you even start the engine and start driving? The is a debate that has started since the concept of A/C in a car was invented, we bust the myth on whether this practice actually makes a difference.

The myth of keeping all accessories off came from back in the day when cars still run on carburetors. This was when the advice to let your engine warm up came to be. But, we've since left carburetors behind and moved on to fuel injection engines, so there's no need to "warm up" your engine anymore.

First off, let’s establish the fact to the “not-so-savvy” car owners reading this article. The car engine and the car A/C are different components but the two systems work hand in hand as they are connected with a belt that will allow the engine to power the A/C compressor.

So, the answer is yes: turning on the A/C immediately after turning on your engine will add a little more stress to the engine when cranking up. This causes the car to vibrate a little harder but it doesn’t mean that any of these components are in trouble.

As expected, the A/C compressor is the most energy consuming component as it encompasses parts like the condenser fan and blower fan. Since it is powered by the engine this puts a lot of mechanical load on the powertrain.

The added mechanical load from the A/C compressor is what causes the added vibration when you switch on the A/C.    

If you find the vibrations unsettling, then the advice is to put the car in gear and start driving before turning on the A/C because doing so will disperse the vibration to the drivetrain instead. 

If you find the vibrations getting harsher as your car gets older, that is due to usual wear and tear of components in your car, especially the engine mounting.

We’ve talked about the engine mounting before, so we know that the mounts are the cause of many vibration and noise level issues.

A worn engine mount will also cause engine components to come into contact with the car body, for the A/C’s case it is the compressor hose, which will cause an uncomfortable grinding sound.

The lifespan of an engine mount really depends on the driving style, check out our story about engine mounts to understand more.

But if you find that your car A/C is making strange noises, most commonly an unsettling squealing, and vibrating harder than normal, this is when you should start worrying.

A worn belt usually causes the squealing in the car. Always ensure that all belts in the engine bay are in good condition, if one of these belts break it would cause devastating effects. This includes the A/C belt as even though the belt only turns the A/C compressor, the belt could get trapped or wedged in unwanted places. 

Other components that needs to be checked include the A/C compressor, pulley, and compressor clutch. Every one of these components needs to be replaced when worn to reduce the vibration on the A/C compressor body.

Conclusion

Starting the car air-conditioning will not cause your car engine to damage quicker. It does cause a little more stress to the engine due to the added mechanical load but it doesn’t cause the engine wear out faster.

The vibration is harsher mostly in older cars as they have already been put to good use for several years and the engine mounting have already done its job absorbing undulations. But this is entirely due to usual wear and tear.

So, if you don’t like the vibration, feel free to leave your A/C off until you have started driving. But if you’re impatient, just know that there won’t be any problems turning it on immediately.