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Home >> Volvo >> 1998 >> C70 Convertible L5-2.3L Turbo VIN 53 B5234T3 >> Repair and Diagnosis >> Powertrain Management >> Computers and Control Systems >> Testing and Inspection >> Component Tests and General Diagnostics >> Checking Air Conditioning (A/C) System >> Checking The Air Conditioning (A/C) System >> Part 1

Part 1






Checking the air conditioning (A/C) system

Introductory check












- Start engine.
- Air conditioning (A/C) switch on.
- Blower fan at low-speed.
- Disconnect the Volvo Scan Tool (ST) from the VIDA station and use it in stand-alone mode.
Make a note of the air conditioning (A/C) compressor and air conditioning (A/C) relay values on the Volvo Scan Tool (ST)
Compare the values with the following fault-tracing table.









- Connect the Volvo Scan Tool (ST) to the VIDA station before continuing fault-tracing.

Select a suitable alternative.

1 - Checking fuse

2 - Checking the power supply to the pressure switch (Pressostat)

3 - Checking the power supply to the compressor

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Checking fuse
- Check that fuse 31 is intact.





Is the fuse intact?

Yes - Connecting the breakout box

No - Checking for a short-circuit

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Checking for a short-circuit




- Check circuit for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.

Continue - Fault-tracing information

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Connecting the breakout box





Connecting breakout box (connector B)

Connecting the breakout box

Is the breakout box connected to the Motronic 4.4 connector?

Yes - No Fault Found

No - Connecting breakout box to Motronic 4.4 connector B (gray)

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Connecting breakout box to Motronic 4.4 connector B (gray)
- Ignition off.
- Disconnect control module.

Note! The engine control module (ECM) must not be removed from the car until the main relay has interrupted its power supply. This may take up to 150 seconds (cars with an immobilizer 245 seconds) after the ignition has been switched off.

Connect adapter 951 1351 ADAPTOR 86-PIN 951 1351 Adaptor 86-Pin to engine control module (ECM) connector and connect breakout box 981 3190 Replaced by 9511428 981 3190 Replaced by 951 1428 to adapter.





Continue - Checking ground terminal #B28

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Checking ground terminal #B28




- Ignition off.
- Switch off all equipment that takes power from the battery (courtesy lighting, radio etc).
- Connect control module.




- Connect an ohmmeter between #28 (#B28) on the breakout box and battery negative terminal.





The ohmmeter should read approximately 0 ohms.

OK - Reading is OK

Not OK - Checking for an open-circuit

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Checking for an open-circuit




- check ground terminals 31/32 and 31/33 on the engine and their cables for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault and contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.

Continue - No Fault Found

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Reading is OK
- Return to the fault-tracing procedure where it was interrupted.

Continue - No Fault Found

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FAULT FOUND - Checking the signal cable

No Fault Found - Checking the signal cable

FAULT-TRACING FAILED - Checking the signal cable

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Checking the signal cable
- Remove glove compartment.
- Disconnect air conditioning (A/C) relay (2/22).




- Connect an ohmmeter between relay base terminal 4 and #40 (#B40) on the breakout box.

The ohmmeter should read approximately 0 ohms.

OK - Checking the power supply to relay base terminal 1

Not OK - Checking for an open-circuit

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Checking for an open-circuit




- Check cable between #B40 and relay base terminal 4 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.





Continue - Fault-tracing information

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Checking the power supply to relay base terminal 1












- Air conditioning (A/C) switch on.
- Ignition on.
- Air conditioning (A/C) relay disconnected.
Connect a voltmeter between relay base terminal 1 and ground.









The voltmeter should read battery voltage.

OK - Checking the power supply to relay base terminal 2

Not OK - Fault-tracing information

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Fault-tracing information
- 1. the car has ECC.
- 2. the car has MCC.

Select one of the above alternatives.

1 - Checking for an open-circuit

2 - Checking the power supply from the air conditioning (A/C) switch

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Checking for an open-circuit




- Check cable between fuse 31 and air conditioning (A/C) relay (2/22) terminal 1 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.





Continue - Fault-tracing information

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Checking the power supply from the air conditioning (A/C) switch








- Ignition off.
- Remove heater controls.
- Air conditioning (A/C) switch on.
- Ignition on.








- Connect a voltmeter between air conditioning (A/C) (3/54) terminal 2 and ground.

The voltmeter should read battery voltage.

OK - Checking for an open-circuit

Not OK - Checking the power supply to the air conditioning (A/C) switch

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Checking for an open-circuit




- Check cable between air conditioning (A/C) switch terminal 2 and air conditioning (A/C) relay terminal 1 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.





Select "Continue" when the fault has been repaired.

Continue - Fault-tracing information

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Checking the power supply to the air conditioning (A/C) switch




- Ignition on.








- Connect a voltmeter between air conditioning (A/C) switch terminal 1 and ground.

The voltmeter should read battery voltage.

OK - Fault-tracing information

Not OK - Checking for an open-circuit

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Fault-tracing information
- Try a new air conditioning (A/C) switch.

Continue - Fault-tracing information

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Checking for an open-circuit




- Check cable between fuse 31 and air conditioning (A/C) switch terminal 1 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.





Continue - Fault-tracing information

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