Leaving the air conditioner running overnight while your vehicle is parked should not directly damage the engine. However, there are a few factors to consider:
Battery Drain: The air conditioner relies on the vehicle's battery to operate when the engine is not running. If you leave it running for an extended period, especially without the engine running, it can drain the battery. This could potentially prevent your vehicle from starting the next time you want to use it.
Fuel Consumption: If the engine is running while the air conditioner is on, it will consume fuel. Running the engine for an extended period without actually driving the vehicle can be wasteful and increase fuel consumption.
Wear and Tear: While the air conditioner itself won't directly damage the engine, running the engine for long periods unnecessarily can contribute to wear and tear on various engine components, such as belts, pulleys, and engine seals.
It's generally recommended to avoid leaving the air conditioner running for an extended period when the engine is off. If you need to cool down your vehicle before driving, it's more efficient to turn on the air conditioner after you start the engine. This allows the air conditioner to draw power from the alternator, which charges the battery while providing electricity to the vehicle's systems.