If you run out of gas while the air conditioner (AC) is on in your vehicle, the AC system will stop functioning shortly after the engine shuts down. The AC compressor, which is driven by the engine's belt, requires power from the engine to operate. When the engine stops running due to lack of fuel, the AC compressor will no longer receive power, and the AC system will cease to cool the air.
Once the engine has stopped, the remaining cool air in the system will gradually dissipate, and the cabin temperature will start to rise, eventually reaching the outside temperature. Without the engine running, the AC system cannot generate cold air, so it will not provide any cooling effect.
It's worth noting that running the AC while the vehicle is not in motion can also have an impact on the battery. If the engine is not running and the AC is drawing power from the battery, it can drain the battery over time. Therefore, if you find yourself in a situation where you have run out of gas, it's generally recommended to turn off the AC to preserve the battery and avoid additional complications.