Can the car air conditioner be turned on with only the power on?
3 Answers
Car air conditioning can be turned on with only the power on. The following is a related introduction to car air conditioning: 1. Compression process: The compressor sucks in the low-temperature and low-pressure refrigerant gas at the outlet of the evaporator and compresses it into high-temperature and high-pressure gas before discharging it from the compressor. 2. Heat dissipation process: The high-temperature and high-pressure superheated refrigerant gas enters the condenser, where the pressure and temperature decrease, causing the refrigerant gas to condense into a liquid and release a large amount of heat. 3. Throttling process: The refrigerant liquid with higher temperature and pressure passes through the expansion device, where its volume increases, and the pressure and temperature drop sharply, discharging from the expansion device in a mist form (fine droplets). 4. Heat absorption process: The mist-like refrigerant liquid enters the evaporator. Since the boiling point of the refrigerant is much lower than the temperature inside the evaporator, the refrigerant liquid evaporates into a gas. During the evaporation process, it absorbs a large amount of surrounding heat, and then the low-temperature and low-pressure refrigerant vapor enters the compressor again.
Having driven for over a decade, I'm quite qualified to speak on this matter. When a car's electrical system is on without the engine running, you can indeed activate the air conditioning's fan function by pressing the AUTO button, which will start the fan. However, the air conditioning compressor doesn't operate in this state, so it only blows natural air or residual warm air, with no cooling effect at all. I once tried this while waiting in the car during summer, and it remained unbearably stuffy inside. Moreover, running just the fan with the electrical system on for extended periods drains the battery significantly, risking a dead battery that could leave you unable to start the car. So, for real cooling, you need to start the engine. Especially nowadays, with many cars featuring automatic air conditioning, turning on the electrical system without the engine actually worsens the effect. It's advisable to start the vehicle, adjust to a comfortable temperature, and then turn on the air conditioning for both peace of mind and energy efficiency.
This issue stems from automotive design. Running the air conditioning in the power-on-only state can be divided into two scenarios: For automatic AC, pressing AUTO allows the fan to operate, but the compressor requires engine power, so it won't cool at all; for manual AC, pressing the button may light up the AC indicator misleadingly, while the compressor remains inactive. As a mechanic, I've encountered owners complaining about no cold air, only to find they had powered on without starting the engine. This state can also accelerate battery drain, especially in older vehicles where the battery might not last half an hour. Worse still, some models may trigger fault codes requiring specialized clearing. Unless you genuinely just need ventilation, avoid doing this at all costs.
