I want to know which part of AC needs to be replaced.

Hi, my name is Devin. I am an auto repair expert with the Car Genius team here at RepairPal. I'm sorry to hear you're having trouble with your Crosstrek. Based on what you're describing, it sounds like you could have an issue with the A/C amplifier, control unit, or an actuator on the HVAC box. In some cases, there may be codes stored in the air conditioning computer that may point toward a faulty component. Having diagnostic tests performed at a trusted shop should pinpoint the issue. If you need more advice, have any other questions about your vehicle, or would like to get connected to a RepairPal Certified shop near you, we have you covered. Give us a call at 877-913-1554, and we will happily help you out!