Motor Expo 2026

Engine started, can turn on the AC right away!...or...? 
 
They say... : When starting the engine for the first time while it's still cold, can you turn on the AC right away? Is it true?

True : When starting the engine for the first time, you can turn on the AC immediately, or even turn it on simultaneously with starting the engine, if the battery is still in good condition. 

If you are driving without the AC on and decide to turn it on, you should not turn it on when the engine is running at high RPM. You should turn on the AC (compressor working) at low engine RPM first, for about 10-15 seconds. 

When starting the engine for the first time, after it has been parked overnight for many hours, you can turn on the AC immediately after starting the engine, without waiting for the engine to reach operating temperature. This is because the AC system is not related to the water in the radiator, which would require waiting for the engine to heat up to operating temperature first. Even starting the engine with the AC switch left on can be done, if the battery still has good power.

To be correct, and to extend the lifespan of the AC system (especially the compressor) for a long time, you should turn on the AC system every time after the engine has started. This is because when starting the engine, the starter should not have to exert force to drive the compressor simultaneously, even though it is possible. Moreover, if your car's battery power is already weak, what was just "manageable" will become "unmanageable" immediately. 

In newer car models with automatic AC systems that control the compressor to operate when the engine speed is sufficient, if you leave the AC switch on when starting the engine, the compressor will not operate. If your car is like this, you can leave the AC on. However, what needs special emphasis is the case where you are driving without the AC on and decide to turn it on, you should not turn it on when the engine is running at high RPM, because the compressor lubricant oil would have all flowed down to the bottom sump. You should turn on the AC (compressor working) after a long stop, at low engine RPM first, for about 10 to 15 seconds is enough. 

From the moment you start the engine, fasten your seatbelt, check fuel level, ensure everything is in order, engage gear, by then the oil inside the compressor will have been lubricated and ready to work. 

Cr. Witwin Traiphit Formula