Home ReviewsRefund
Home/Lincoln/Mark VII/Lincoln Mark VII I (1984-1992)/Repair manual/Headlights/Headlights - Automatic
Contents Section: Headlights All sections

Headlights - Automatic Lincoln Mark VII I

Headlights 1 illustration ~1095 words

DESCRIPTION & OPERATION

The automatic headlight dimmer is a driver-controlled electronic device which automatically switches the headlights from high to low beam in response to headlights from oncoming vehicles or taillights from a vehicle being overtaken. The system consists of a sensor-amplifier, a high-low beam relay, a flash-to-pass relay, a dimmer switch, a dimmer range control and an indicator light.

SENSOR-AMPLIFIER

The sensor-amplifier unit combines a light-sensing optical device and transistorized amplifier mounted on the rear view mirror support. Sensitivity is adjusted at the factory and the unit is sealed in epoxy to prevent further adjustment.

POWER RELAYS

The power relays provide heavy duty contacts for switching the headlight beams. The high-low beam relay and the flash-to-pass relay are identical. Both relays are mounted under the instrument panel. To protect the sensor amplifier, the relays contain a diode for damping purposes. Observe proper polarity when connecting relays to prevent diode damage.

RANGE CONTROL

The dimmer range control is the first dial to the right of the headlight switch. It allows the driver to adjust the system sensitivity. Rotating the thumbwheel upward toward maximum "ON" position increases sensitivity. Headlights will dim when vehicles are at a greater distance away.

Rotating thumbwheel downward decreases sensitivity, allowing approaching vehicles to come nearer before headlights dim. Moving thumbwheel downward to "OFF" position permits manual operation of headlight beams with the column dimmer switch.

DIMMER SWITCH

The dimmer switch used is a special flash-to-pass type located in the steering column. One position provides low beam operation; the other provides automatic operation. Moving lever half-way between positions allows the driver to flash high beams.

SENSOR-AMPLIFIER VERTICAL AIMING

Sensor-amplifier horizontal and vertical aim is factory pre-set and not adjustable. Horizontal aiming is pre-set 2 degrees left of the horizontal plane. Sensor-amplifier units are color coded for correct application. When replacement is necessary, be certain to use Blue label for Continental; Green label for Town Car; and Orange label for all others.

AUTODIMMER INDICATOR INOPERATIVE

Burned out bulb. Defective dimmer switch or wiring.

HEADLIGHTS STAY ON LOW

Defective sensor-amplifier. Defective relay or dimmer switch. Wiring problem.

HEADLIGHTS STAY ON HIGH BEAM

Defective sensor-amplifier. Damaged high-low beam relay.

HEADLIGHTS DIM TOO SOON OR TOO LATE

Driver control adjustment. Dirty sensor lens, chamber or windshield. Loose amplifier or support. Defective sensor-amplifier. Damaged potentiometer.

NO FLASH-TO-PASS

Defective dimmer switch, relay or wiring. Blown fuse in fuse block.

NO MANUAL LOW BEAM

Defective high-low relay. Defective dimmer switch or wiring. Defective flash-to-pass relay.

PREPARATION FOR TESTS

The transistorized unit needs no warm-up time. Place car in a lighted area, adjust sensitivity control to a central position, and operate engine at a fast idle to maintain constant voltage.

SYSTEM TEST PROCEDURE

  1. Turn headlight switch to "ON" position. If headlights remain on low beam in both positions of the dimmer switch, proceed to step 7). If headlights do not remain on low beam, proceed to next step.
  2. Remove high-low relay. Connect one lead of test light to battery voltage and other lead to Violet wire of relay connector. If test light does not light for both positions of dimmer switch, replace relay.
  3. If test light does light, remove dimmer switch connector. If test light remains lighted, repair short in circuit. If test light indicates no voltage, replace dimmer switch and reconnect relay.
  4. Disconnect sensor-amplifier cable at in-line connector. Connect voltmeter between ground and White wire at sensor. With sensitivity control fully clockwise and headlights on, meter should read battery voltage.
  5. Rotate control fully counterclockwise. Meter should read zero volts. Rotate control between the 2 positions. A smooth, continuous voltage change should be indicated. If control does not operate as described in steps 4) and 5), replace sensitivity control.
  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 raising dimmer switch. Headlights should switch to high beam. If headlights do switch to high beam, proceed to step 9). If headlights do not switch to high beam, check for loose connection at high-low relay, dimmer switch connector near driver sensitivity control, or check in-line connector between sensor-amplifier cable and wiring harness.
  8. Disconnect Red wire from dimmer switch connector and ground it to vehicle body. If headlights switch to high beam, replace dimmer. If headlights do not switch to high beam, reconnect Red wire and check continuity of circuit through harness to sensitivity control and sensor-amplifier.
  9. Place dimmer switch in "AUTOMATIC" position and tightly cover sensor-amplifier lens with a Black cloth. Headlights should switch to high beam. Remove cloth and proceed to step 11). If lights do not switch to high beam, disconnect sensor-amplifier at in-line connector.
  10. Ground Gray/Yellow Dot wire on engine compartment wiring harness connector. 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 sensitivity control fully counterclockwise. If headlights do not switch to high beam, check sensitivity control for poor connection to ground. If headlights do switch to high beam, proceed to next step.
  12. If system responds correctly to all tests, unit is functioning properly and only sensitivity and aiming remain to be checked.

AUTOMATIC DIMMER SWITCH

  1. Connect an ohmmeter to terminals No. 1 and 2 on back of potentiometer. (Scheme 1) With thumbwheel in "OFF" position, ohmmeter should read 8000-12,000 ohms. Rotate thumbwheel to maximum "ON" position. Ohmmeter should read 2800-4600 ohms.
  2. Connect ohmmeter to terminals No. 3 and 6. There should be continuity with thumbwheel in "OFF" position and no continuity in other positions.
  3. Connect ohmmeter to terminals No. 2 and 6. With thumbwheel in "OFF" position, ohmmeter should read 8000-12,000 ohms. With thumbwheel in other positions, ohmmeter should read about 100 ohms. If ohmmeter reads greater than 8000-12,000 ohms, replace indicator bulb.

Scheme 1

Scheme 1
Scheme 1

Removal & Installation

Disconnect battery ground cable. Remove steering column shroud. Disconnect dimmer switch lever by pulling out of switch with a twisting motion. Remove foam backing from switch. Remove connectors and screws. Remove switch. To install, reverse removal procedure.

Disconnect battery ground cable. Remove pad below steering column. Remove lower cluster lens and left side finish molding. Remove lower left side pad. Remove relay from instrument panel brace and disconnect relay from connector. To install, reverse removal procedure.

Disconnect plug at rear of unit. Remove mounting screw and remove unit. To install, be certain mirror support is tight. Position sensor-amplifier on support and tighten screw. Install electrical connections.