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924 & 944 Series

  1. Disconnect harness plugs at control unit. The control unit is located in the driver's footwell, behind the center console. The following tests should be made at the harness plugs. Plug No. 1 is from the switch control. Plug No. 2 goes to the servo unit. Plug No. 2 may be identified by the lack of a No. 3 terminal pin. See Figure .
  2. Check plug No. 1 with a voltmeter. Turn ignition switch to "ON" position. Terminal No. 4 should have battery voltage. Terminal No. 8 is a permanent ground. Use it to test plug terminals.
  3. Terminal No. 2 should receive battery voltage when brake pedal is depressed. If not, check brake switch. Check terminal No. 3 for battery voltage. When control switch is slid inward, to "OFF" position, voltage should be zero.
  4. Check terminal No. 5 for battery voltage when push button switch is pushed. Check terminal No. 6 for voltage when sliding switch is moved outward to "ON/SET" position.
  5. Connect tester between terminals No. 4 and No. 7. Battery voltage should be present until clutch is depressed and circuit is opened. If the above circuits do not meet testing specifications, repair or replace switches and wiring as necessary. If defective control unit is suspected, test by substitution.
  6. Connect tester between battery positive (+) and terminal No. 1. With ignition off, voltage should be one volt less than battery voltage. With ignition on, zero voltage should be present. Operate vehicle at 30 MPH. Voltage should be approximately 4 volts. Check that voltage increases with vehicle speed.
  7. Use an ohmmeter to check the following circuits of plug No. 2. Resistance between terminals No. 1 and No. 2 should be 30-40 ohms.
  8. Resistance between terminals No. 4 and No. 7 should be 2-4 ohms. Resistance between terminals No. 4 and No. 8 should be 2-4 ohms.
  9. Resistance between terminals No. 5 and No. 6 should be 20-30 ohms. If servo unit resistance does not meet specification, and unit is suspect, test by substitution.
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