Checking Pressure Switch (Pressostat)

Fig 1: Identifying Ignition OFF

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Fig 2: Disconnecting Connector

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• Ignition off.
• Disconnect the pressure switch (Pressostat) connector.

  Connect an ohmmeter to both pressure switch (Pressostat) terminals.

  Fig 3: Identifying Canister Purge Valve Terminals

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  Fig 4: Identifying Ohmmeter

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The ohmmeter should indicate approximately 0 ohm. 

• NOT OK 

  Refer to Checking Pressure On Low Pressure Side 

• OK 

  FAULT NOT FOUND:  Troubleshooting has been completed.

Fig 1: Engine Start Verification

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Fig 2: Disconnecting Connector

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• Filling point low pressure side (blue hose) connected to service valve.
• Engine idling.
• Switch blower fan switch to position 0.
• Switch air conditioning (A/C) switch to off.
• Disconnect the pressure switch (Pressostat) connector.

  Start the compressor by connecting the magnetic clutch cable to the battery positive terminal.

  WARNING: The compressor may be connected like this for a maximum of 3 minutes.

  Connect an ohmmeter over both pressure switch (Pressostat) terminals.

  NOTE: If the pressure falls below 140 kPa, but the ohmmeter continues to display 0 Ω, stop and disconnect the compressor.
  Fig 3: Identifying Canister Purge Valve Terminals

  Courtesy of VOLVO CARS OF NORTH AMERICA.
  Fig 4: Identifying Ohmmeter

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  Fig 5: Identifying Blower Fan Switch And Air Conditioning (A/C) Switch

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The ohmmeter should read infinite resistance at a compressor pressure of 150-170 kPa. 

• NOT OK 

  Refer to Replacing Component 

• OK 

  Refer to Fault-Tracing Information