The HVAC Scan Tool Data Definitions contains a brief description of all HVAC related parameters available on the scan tool. The list is in alphabetical order. A given parameter may appear in any one of the data lists. In some cases, the parameter may appear more than once or in more than one data list in order to group certain related parameters together. All parameters may not apply to every vehicle. Use only the parameters which apply to your particular vehicle.

A/C Evaporator Switch: The scan tool displays Open or Closed. The A/C evaporator switch is an input to the PCM that determines when pressure has reached a calibrated threshold. The PCM uses this switch as the primary input for determining when to command the A/C compressor ON or OFF.

A/C Sec. High Pressure Switch: The scan tool displays Open or Closed. The secondary high pressure switch closes when the A/C system's high pressure limit is approached. The PCM monitors the state of this switch for compressor and auto recirculation operation. The switch closes at a high pressure value which is calibrated for specific platforms. The PCM continuously monitors the secondary high pressure switch when A/C has been selected by the operator.

A/C Relay: The scan tool displays On or Off. On is displayed when the PCM has energized the A/C compressor clutch relay.

A/C Request: The scan tool displays Yes or No. The PCM uses the A/C request signal in order to determine whether A/C compressor operation has been requested by the operator.

HVAC Switch In Recirculation Mode: The scan tool displays Yes or No. The PCM uses this information to control A/C compressor clutch cycling.