Because of its location, replacing it often requires partially dismantling the HVAC system or at least accessing the blower motor assembly. A mechanic's manual specific to your vehicle year and model would be extremely helpful in pinpointing its exact position within that harness. A diagram showing the wiring would be invaluable.
Without that manual, locating it visually is extremely difficult. It's better to bring it to a mechanic if you suspect this switch is faulty.
