A very common issue
The car AC evaporator works by absorbing heat from the passenger compartment of the vehicle and also removing moisture from the air - making it very useful in the winter with cold frosty mornings or damn evenings.
The evaporator is located inside the vehicle, making access difficult and involved removing the dashboard and surrounding fittings. It is connected to the refrigerant line from the AC compressor.
The car AC evaporator is essentialy a heat exchanger like the the condenser but is much smaller in size.
Some vehicles, usually MPVs, minivans or SUVs have two evaporators which may be under the instrument panel, or at the front of the vehicle, another maybe located in or toward the rear of the vehicle. The rear evaporator is often located behind a side panel or roof mounted above the rear passengers.
Popular right now for evaporator replacement & AC repair : -
Mercedes Viano
Ford Focus