Evaporator

How you know it is this

• A persistent musty or sour smell from the vents
• Gradual loss of cooling with no leak found anywhere accessible
• Water inside the car rather than dripping underneath — a blocked drain
• Oily residue in the condensate

Worth knowing before you buy

• The part is moderate and the job is not — the dashboard usually has to come out, which is a day or more.
• Because of that, be certain. An evaporator leak is diagnosed with a detector at the vents or with dye, not by elimination.
• THE SMELL IS USUALLY NOT THE EVAPORATOR. It is bacteria on a damp fin surface, and a proper clean plus a new cabin filter fixes it for a fraction of the cost.
• A blocked condensate drain floods the passenger floor and is mistaken for a heater matrix leak. The water is clear and odourless — that is how you tell.

Rest of the refrigerant circuit

• A/C compressor
• A/C compressor clutch and coil
• Condenser
• Receiver drier / accumulator
• Expansion valve
• A/C pipes and hoses
• Pressure switches and sensors
• Refrigerant and oil