Before installing the HVAC pressure switch, first coat a new rubber O-ring seal (4) with clean refrigerant oil and put it on the A/C discharge line (3). After that, place the HVAC pressure switch (2) onto the A/C discharge line and attach the wire harness connector (1) to the HVAC pressure switch. When finished, attach the top of the front fascia and then link up the negative
Battery Cable. Make sure the O-ring for the R-134a refrigerant is specially made and that you are using the needed refrigerant oil in the A/C compressor.