DESCRIPTION & OPERATION
The automatic headlight dimmer switches the headlights from high to low beam in response to headlights from oncoming vehicles and taillights from vehicles being overtaken. Principal components of the system are a sensor-amplifier, high-low beam relay, dimmer switch, dimmer range control and indicator light.
DIMMER SWITCH
The flash-to-pass dimmer switch is located in the steering column. One switch position provides low beam operation and the other provides automatic operation. Momentarily placing dimmer switch lever halfway between positions flashes high beams.
HIGH-LOW BEAM RELAY
The high-low beam relay switches the headlight beams. It is controlled by the dimmer switch or by the sensor-amplifier.
DIMMER RANGE CONTROL
The dimmer range control adjusts system sensitivity to surrounding light. Rotating the control toward maximum ON position increases sensitivity; headlights dim when approaching vehicles are at a greater distance. Setting control to OFF position permits manual operation of headlight beam with column dimmer switch.
SENSOR-AMPLIFIER
The sensor-amplifier senses light from oncoming headlights or from taillights of vehicles ahead. The unit is adjusted for aim and sensitivity at the factory, and is then sealed with epoxy. The epoxy prevents access to factory sensitivity adjustments and interior parts.
Note. If an automatic headlight dimmer malfunction cannot be immediately serviced, manual operation of headlights may be obtained at the dimmer switch by disconnecting sensor-amplifier and turning dimmer range control to the OFF position.
SENSOR-AMPLIFIER HORIZONTAL & VERTICAL AIMING
Sensor-amplifier horizontal and vertical aim is preset at factory and is not adjustable. Horizontal aiming is preset at 2 degrees left.
Autodimmer Indicator Inoperative
Check for burned-out bulb, and replace if necessary. Check for defective switch in potentiometer assembly and defective dimmer switch. To do so, turn headlights on, and set dimmer switch to automatic position. Check for battery voltage at Yellow wire of potentiometer connector. If battery voltage exists, replace potentiometer assembly. If voltage does not exist, check dimmer switch and wiring.
No High Beam With Dimmer Range Control Turned Off
Check for defective high-low beam relay, and replace if necessary. Check dimmer switch for proper operation.
No High Beam When System Is On Automatic
Check for loose connections and poor grounding at sensor-amplifier. Check for defective sensor-amplifier. To do so, move dimmer range control to minimum range without turning it off. Hold a black cloth directly over sensor amplifier lens. Sensor is defective if it does not switch to high beam within a few seconds.
Only High Beam When System Is On Automatic
Check for defective high-low beam relay; replace if necessary. Check for defective sensor-amplifier. To do so, turn headlights on. Ensure sensor is exposed to sufficient light and dimmer switch is in automatic position. Disconnect sensor-amplifier connector. If headlights return to low beam, replace sensor-amplifier.
Headlights Dim Too Soon Or Too Late
Check for loose amplifier or mirror support, and tighten as required. Check for defective potentiometer or sensor-amplifier. See AUTOMATIC HEADLIGHT DIMMER SYSTEM TEST under TESTING. If headlights dim too late, clean windshield and retest.
No Flash-To-Pass
Check for blown fuse or circuit breaker. Replace fuse in position No. 14 if necessary. Check for defective dimmer switch.
No Manual Low Beam
Check for defective high-low beam relay. To do so, remove high-low beam relay, and check for continuity between Red/Yellow wire (circuit No. 15) and Red/Black wire (circuit No. 13). Check for defective dimmer switch. To do so, disconnect dimmer switch. If headlights return to low beam, replace dimmer switch.
PREPARATION FOR TESTING
Place car in a well-lit area. Set dimmer range control to approximate center of its range. Operate engine at fast idle to maintain constant voltage.
AUTOMATIC HEADLIGHT DIMMER SYSTEM TEST
- Set headlight switch to ON position. Set dimmer switch to high beam position. Set dimmer sensitivity to maximum. Locate sensor at center of windshield header, behind rearview mirror. Using a paper clip, push self-test button through hole in top right of sensor.
- Headlights should switch to low beam and back to high beam position within 5 seconds. If headlights do not switch, check circuit No. 508 (White wire between dimmer sensor and control switch) for short to ground.
- If headlights do not return to low beam, replace sensor. If system still does not operate, continue testing.
- Start engine, and operate it at fast idle. Set dimmer sensitivity to approximate midpoint of its travel. Headlights should remain in low beam in both positions of dimmer switch when sensor is exposed to sufficient light. If headlights do not function as specified, go to step 5). If headlights function as specified, go to step 9).
- If headlights remain in high beam, remove high-low beam relay. High-low beam relay is located behind center of instrument panel on Continental and Mark VII and above steering column on Town Car. Connect test light between Gray/Yellow wire at relay connector and battery voltage. If test light does not glow at each position of dimmer switch, replace relay.
- If test light glows at each position of dimmer switch, unplug dimmer switch connector. If test light continues to glow, check for short in circuit No. 505 (Gray/Yellow wire). If wire is okay, replace dimmer switch. Reconnect relay.
- Disconnect sensor-amplifier cable at in-line connector. Connect DVOM between ground and White wire (circuit No. 508) at sensor. With dimmer range control knob fully clockwise and headlights on, meter should indicate approximately battery voltage.
- Rotate dimmer range control knob fully counterclockwise. DVOM should indicate zero volts. Rotate knob between both positions. A smooth, continuous voltage change should occur. Replace dimmer range control if it does not operate as described in steps 7) and 8).
- 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.
- Activate flash-to-pass system by momentarily placing dimmer switch halfway between low beam and automatic positions. Headlights should switch to high beam. If headlights switch to high beam, proceed to step 11). 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.
- 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.
- Set dimmer switch to automatic position. Cover sensor-amplifier lens using a black cloth. If headlights switch to high beam, remove cloth, and go to step 14). If headlights do not switch to high beam, disconnect sensor-amplifier at in-line connector.
- Ground Gray/Yellow 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.
- Set dimmer switch to automatic low beam. Rotate dimmer range control 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, unit is functioning properly. Check sensitivity and aiming.
REMOVAL & INSTALLATION
| CAUTION | When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in the GENERAL INFORMATION section before disconnecting battery. |
Dimmer switch is part of multifunction switch on steering column. Disconnect negative battery cable. Remove steering column trim shroud. Remove connectors and screws. Remove switch. To install, reverse removal procedure.
High-low beam relay is located on relay panel behind center of instrument panel on Continental and Mark VII and above steering column on Town Car. Disconnect battery ground cable. Unplug relay from connector. To install, reverse removal procedure.
Unplug connector at rear of unit. Remove mounting screw. Remove unit from mirror support. Reverse removal procedure to install. Ensure mirror support is tight.
WIRING DIAGRAMS
Note. Due to the size and complexity of the Wiring Diagrams it is recommended that the Diagram be printed.
The following diagram is for: Continental
Automatic Headlight System (Grid B-E 32-35). Scheme 1
The following diagram is for: Mark VII
Automatic Headlight System (Grid B-C 16-19). Scheme 2
The following diagram is for: Town Car
