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Automatic Headlight Dimmer System Test

  1. Turn headlight switch to ON position. Expose sensor to sufficient light. Headlights should remain in low beam position for both positions of dimmer switch. If headlights remain on low beam in both positions of dimmer switch, proceed to step 7).
  2. If headlights remain in high beam position for both positions of dimmer switch, remove high-low beam relay from its connector. See HIGH-LOW BEAM & FLASH-TO-PASS RELAYS under REMOVAL & INSTALLATION. Connect one lead of test light to battery voltage and other lead to Yellow/Gray wire of relay connector. See Figure -6. If test light does not light for both positions of dimmer switch, replace relay.
  3. If test light lights, remove dimmer switch connector. If test light remains lit, check for short in circuit No. 505. If no short, replace dimmer switch, and reconnect relay.
  4. Disconnect sensor-amplifier cable at in-line connector. Connect voltmeter between ground and White wire (circuit No. 508) at sensor. With dimmer range control thumbwheel fully upward (knob fully clockwise) and headlights on, meter should read approximate battery voltage.
  5. Rotate dimmer range control thumbwheel fully downward (knob fully counterclockwise). Meter should read zero volts. Rotate thumb-wheel between both positions. A smooth, continuous voltage change should be indicated. Replace dimmer range control if it does not operate as described in steps 4) and 5).
  6. With headlights on, sensor exposed to sufficient light and dimmer switch in automatic position, disconnect sensor-amplifier cable at in-line connector. If headlights return to low beam, replace sensor-amplifier. If headlights remain on high beam, replace dimmer switch.
  7. Activate flash-to-pass system by momentarily moving dimmer switch half-way between low beam and automatic positions. Headlights should switch to high beam. If headlights switch to high beam, proceed to step 9). If headlights do not switch to high beam, check for loose connection at high-low beam relay, dimmer switch connector, and at in-line connector between sensor-amplifier cable and wiring harness.
  8. Also disconnect Red wire (circuit No. 527) from dimmer switch connector, and ground it to vehicle body. If headlights switch to high beam, replace dimmer switch. If headlights do not switch to high beam, reconnect Red wire, and check continuity of circuit through harness to dimmer range control and sensor-amplifier.
  9. Move dimmer switch to automatic position, and cover sensor-amplifier lens with a black cloth. Headlights should switch to high beam. Remove cloth and proceed to step 11). If headlights do not switch to high beam, disconnect sensor-amplifier at in-line connector.
  10. Ground Gray/Yellow dot wire (circuit No. 505) on male connector at dimmer range control. If headlights switch to high beam, replace sensor-amplifier. If headlights do not switch to high beam, replace dimmer switch.
  11. Place headlights on automatic low beam, and rotate dimmer range control's thumbwheel fully downward (knob fully counterclockwise). If headlights do not switch to high beam, check dimmer range control for poor connection to ground. If headlights switch to high beam, proceed to next step.
  12. If system responds correctly to all tests, unit is functioning properly. Check sensitivity and aiming.
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