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928 Series

  1. Disconnect harness plug at control unit. The control unit is located beneath the dash, on the passenger side. The following tests should be made at the harness plug. See Figure .
  2. With ignition switch in "ON" position, check for battery voltage at terminal No. 5. Terminal No. 12 is permanent ground. Use this terminal for testing procedures.
  3. Check for battery voltage at terminal No. 6 when brake pedal is depressed. Check for battery voltage at terminal No. 8. Voltage should drop to zero when control lever is pulled toward steering wheel.
  4. Battery voltage should be present at terminal No. 9 when control lever is pushed forward. Check for battery voltage at terminal No. 10 when switch lever is moved downward.
  5. Turn ignition off. Use an ohmmeter to check resistance of vacuum servo unit between terminals No. 3 and No. 7. Resistance should be 14 ohms.
  6. Terminal No. 11 should receive a pulse signal when speedometer moves. Rotate one rear wheel and check with ohmmeter. If circuits test to specification and system is inoperative, suspect defective control unit. Test by substitution.
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