Air-conditioning trinary switch for all TVR models with air-conditioning. This switch controls a number of functions of the air conditioning system and is mounted in the receiver drier. As with most work on the air-conditioning system the refrigerant will need to be removed prior to replacing the switch.The trinary switch contains three pressure switches; high, low and medium. The trinary switch has three functions: 1. To disengage the A/C compressor clutch if the refrigerant pressure falls below the "minimum" specified value. 2. To disengage the A/C compressor clutch if the refrigerant pressure exceeds the "maximum" specified value. 3. To switch the cooling fan to high speed if the refrigerant pressure exceeds the "high" specified value. This is a high quality trinary switch and comes with the correct o ring ready for fitting. Should the trinary switch require replacement or the system opened then the reveiver drier unit should also be changed.