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Home >> BMW >> 1986 >> 635CSi Standard >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Cruise Control Systems >> Testing >> Cruise Control System

Cruise Control System

  1. Check fuse and contacts. Replace fuse or clean contacts as required. Check stop light bulbs and contacts. Replace bulbs or clean contacts as required. Ensure cruise control cable is properly adjusted and not damaged. Ensure motor and strap operate with easy movement.
  2. Ensure brake and clutch switches are properly adjusted. Check all wires and wiring connectors for damage and proper fit. Repair or replace as required.
    NOTE: Steps 3) through 10) are performed with wiring connector disconnected at cruise control unit.
  3. Using an ohmmeter, measure resistance value between ground and terminal No. 23 of connector. If reading is not zero ohms, repair ground connection.
  4. Turn ignition on. Using a voltmeter, measure voltage between ground and terminal No. 1 of connector. Voltmeter should display battery voltage. If battery voltage is not displayed, repair power supply circuit.
  5. Turn ignition on. Using a voltmeter, measure voltage between ground and terminal No. 2 of connector. Voltmeter should display battery voltage. If voltage is not as specified, check and repair cruise control switch, control unit, or wiring. Move cruise control switch to "OFF" position. Voltage reading should now be zero volts. If voltage reading is not as specified, replace cruise control switch.
  6. Turn ignition on. Using a voltmeter, measure voltage between ground and terminal No. 4 of connector. Voltmeter should display battery voltage. If voltage is not as specified, check and repair cruise control switch, control unit, or wiring. Hold switch in "CONSTANT" position. Voltage reading should be battery voltage. If voltage reading is not as specified, replace cruise control switch.
  7. Turn ignition on. Using a voltmeter, measure voltage between ground and terminal No. 5 of connector. Voltmeter should display zero volts. If voltage is not as specified, check and repair cruise control switch, control unit, or wiring. Hold switch in "RESUME" position. Voltage reading should now be battery voltage. If voltage reading is not as specified, replace cruise control switch.
  8. Turn ignition on. Using a voltmeter, measure voltage between ground and terminal No. 9 of connector. Voltmeter should display zero volts. If voltage is not as specified, replace brake switch.
  9. With ignition on and voltmeter connected as in step 8), depress brake pedal. Voltmeter should display battery voltage. If voltage reading is not as specified, pull both plugs from stop light switch. Connect ohmmeter and depress brake pedal. Ohmmeter reading should display zero ohms. Repeat procedure for clutch switch. Replace switch if readings are not as specified.
  10. Connect frequency meter between terminal No. 3 and 6 of connector. Raise vehicle and start engine. Place vehicle in gear and increase speed to about 30 MPH. Frequency reading should be about 84 Hz. If reading is not as specified, check speed transmitter and wiring.
  11. Connect wiring connector to cruise control unit and disconnect 7-pin wiring connector. Connect voltmeter between terminals No. 3 and 4. Turn ignition on. Voltage reading should be about 8 volts. If reading is not as specified, replace control unit.
  12. With 7-pin connector disconnected, connect voltmeter between terminals No. 3 and 7. Turn ignition on. Voltage reading should be about 8 volts. If reading is not as specified, replace cruise control motor.
  13. With 7-pin connector disconnected, apply battery voltage to terminal No. 6 (Green wire), and ground No. 1 terminal (White wire). Cruise control motor clutch should be heard to switch. If not, replace motor.
  14. With 7-pin connector disconnected, apply battery voltage to terminal No. 5 (Black wire) and ground pin No. 2 (Blue wire). Cruise control motor should operate. If not, replace motor.
  15. If steps 12) through 13) test okay, replace control unit.
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