Is there a relay turn the air conditioner on?

Yes, there is usually a relay that turns the air conditioner on. This relay is typically located in the fuse box under the hood of the car. It is responsible for providing power to the air conditioner compressor, which then circulates refrigerant through the system to cool the air. When the air conditioner is turned on, the relay sends a signal to the compressor to start it up. When the air conditioner is turned off, the relay cuts off power to the compressor, causing it to stop running.