The main parts of the air conditioner system include the expansion valve, evaporator coil, condenser coil, and compressor. If one, or all of these parts is not functioning at optimal capacity, this poses a major challenge to keeping your home at your preferred temperature. The expansion valve is needed in order to manage how much liquid refrigerant is operating within the unit. Typically, the cost to replace the expansion valve is around $500, depending on the quality and type, explains Angi.
The evaporator coil is responsible for physically removing overly warm air from inside the property. So this is also a critical piece. The cost to replace the evaporator coil is around $1500 (as noted by Home Advisor). Advanced Heating & Cooling notes that the condenser coil is part of the outdoor unit, and is responsible for eliminating excess warmth from the refrigerant. Typically, this will cost around $1000 to replace but can be well over $2000 in some cases (as noted by Forbes). The compressor is what physically transports the refrigerant around the air conditioning unit. The unit is nothing without this. This Old House notes that replacing this piece costs just under $2000, but can be more depending on the size of the house.