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Home >> Volvo >> 1991 >> 240 SE, AW70L >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Self-Diagnostics - Turbo System >> Control Function No. 3 >> Testing Turbo System Components
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Testing Turbo System Components

  1. Turn ignition on. Locate diagnostic unit and remove its cover. Connect selector cable to socket No. 5. Depress push button 3 times. Each time the button is depressed, it should be held for more than 1 second and less than 3 seconds.
  2. While LED flashes, the cooling fan, turbo control valve and A/C blocking relay should operate. Check by listening or feeling component when it is activated. If turbo control valve does not work, go to step 3). If A/C blocking relay does not work go to step 4). If cooling fan does not operate, check both cooling fan relays. Connect voltmeter between turbo control unit terminal No. 4 and ground. Then between terminal No. 5 and ground. In both cases, reading should be 12 volts.
  3. Connect ohmmeter between turbo control unit terminals No. 1 and 3. Resistance should be 11 ohms. Replace control valve as necessary.
  4. Turn ignition on. Connect voltmeter between turbo control unit terminal No. 6 and ground. Reading should be 12 volts. Turn ignition off. Install turbo connector. Start engine and turn A/C on.
  5. After compressor engages, press accelerator pedal to floor for a short time. Compressor should disengage when throttle is fully open and engage again when throttle closes slightly from fully open position. Replace A/C blocking relay as necessary. Turn ignition off.
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