Headlights - Automatic Ford Thunderbird IX

DESCRIPTION & OPERATION

Autolamp system provides light sensitive automatic on-off control of headlights in conjunction with normal headlight switch operation. A light delay feature is also used to keep headlights on for a pre-selected time period after ignition is turned off and occupant has left vehicle.

Time lapse can be varied up to 4 1/2 minutes before lights turn off automatically. Autolamp system consists of a light sensitive photocell assembly, transistorized amplifier, time delay control which includes an on-off switch and a headlamp control relay.

Autolamp wiring parallels the regular light switch wiring. Headlight switch must be turned "OFF", and autolamp control turned "ON" for system to operate automatically. Autolamp control switch is located next to (Continental, Mark VII, Thunderbird and Cougar) or behind (all other models) headlight switch knob.

In normal operation, system will turn headlights on when natural outside light available to photocell decreases below a predetermined level, such as at sunset. Also, lights will automatically turn off if level of outside light exceeds a predetermined level during daylight hours.

System photocell is mounted under a group of perforated holes in upper instrument finish panel. Turning the autolamp control away from "OFF" position will increase lapsed time before headlights turn off after turning ignition switch off.

SYSTEM OPERATIONAL CHECK

Note. When a system malfunction is unknown, perform following checkout procedure to isolate problem to a specific condition.

1. Ensure that photocell lens of photo amplifier unit is clean and not obstructed. Make sure there is a clean, tight ground connection from circuit 57 of potentiometer unit at headlight switch.
2. Make sure headlights operate normally with headlight switch. Check that autolamp relay connector is properly attached to relay.
3. Place autolamp control in "OFF" position. Turn headlights on using headlight switch. If lights do not operate, check out and correct the standard headlight circuit.
4. If lights work okay, check autolamp fuse. If fuse is okay, proceed to complete system checkout procedures.

CIRCUIT TESTS

Note. Refer to illustrations for connector and terminal identification.

Tail Light Circuit

Remove connector from autolamp relay. Connect a test lamp between ground and Brown wire. Voltage should be present with headlight switch in "PARK" or "ON" position. If not, check continuity of wire to headlight switch.

Headlight Switch & Potentiometer Assembly Crown Victoria, Grand Marquis & Town Car shown; other models similar. Scheme 1

Headlight Circuit

Remove connector at autolamp relay. Connect a test lamp between ground and the Red/Yellow wire. Voltage should be present with switch in the "ON" position. If not, check continuity to headlight switch, and if equipped, to high-low beam relay.

On-Off Control Switch

1. Using test light, test system ground. Connect one lead to ground and other lead to circuit 220 in delay control switch, with switch in "ON" position. If no continuity, perform steps 1) and 2) of Potentiometer test.
2. If potentiometer test is okay, check circuit 220 between potentiometer connector and amplifier connector.

Delay Control Test

1. Connect an ohmmeter between terminals 220 and 217 of the autolamp connector. (Scheme 3) With control in "MAX" position, reading should be approximately 200,000 ohms. If not, perform step 3) of the Potentiometer test.
2. If potentiometer is okay, check circuit 217 for continuity between potentiometer connector and amplifier connector. If potentiometer does not check out okay, replace potentiometer.
3. If all systems check out okay, but system is still malfunctioning, replace the amplifier assembly.

Autolamp Connector Terminal Identification. Scheme 2

Potentiometer Test (Continental, Mark VII Thunderbird & Cougar)

1. Connect a test lamp or ohmmeter to terminals 6 and 4 on back of potentiometer. (Scheme 2)
2. Check that there is no continuity when switch is "OFF" and that there is continuity when switch is in any other position.
3. Connect ohmmeter to terminals 5 and 6. Check that resistance gradually increases from 2500-4500 ohms at "OFF", to 140-260K ohms at "MAX".
4. If potentiometer fails any of the preceding tests, replace the potentiometer assembly.

Potentiometer Test (All Other Models)

1. Using test light, test for continuity between potentiometer connector circuit 57 and switch bracket. (Scheme 2) If no continuity exists, replace potentiometer.
2. Check continuity between circuits 220 and 57 of the potentiometer connector while rotating the switch from "OFF" to "ON".
3. Check continuity between circuits 217 and 57 while rotating switch from "OFF" to maximum time delay. Resistance for these tests should gradually increase from 2500-4500 ohms at "OFF", to 140-260K ohms at maximum time delay.
4. If potentiometer fails any of the preceding tests, replace the potentiometer assembly.

Potentiometer Connector Terminal Identification. Scheme 3

Note. If any part of the control switch test is unsatisfactory, replace potentiometer.

SENSOR AMPLIFIER

Two different amplifiers are used. Both have a label on the case providing adjustment instructions.

HEADLIGHT CONTROL RELAY

1. Locate relay under right corner of instrument panel on Continental, under instrument panel on Cougar, Mark VII and Thunderbird, under instrument panel above ashtray on Crown Victoria and Grand Marquis, on lateral shake brace on LTD and Marquis, and on front upper edge of lower access hold in left hand cowl panel on Town Car.
2. Disconnect battery ground. Remove cowl trim panel on Town Car. On all models, remove screws attaching relay to mounting surface. Disconnect connector and remove relay. To install, reverse removal procedure.

Remove instrument panel top pad. Lift off pad and remove 2 screws holding sensor amplifier to instrument panel. Remove connector. Reverse removal procedure to install sensor amplifier.

HEADLIGHT SWITCH & POTENTIOMETER

Note. Either headlight switch or potentiometer can be replaced separately. Both units must be removed as an assembly on all models except Continental, Mark VII, Thunderbird and Cougar. The assembly is serviced from the front of the instrument panel on those models.

1. Disconnect battery ground. Remove headlight knob, bezels, and switch. Remove plastic spacer at end of potentiometer by pushing out with screwdriver.
2. Remove strap securing wiring harness to switch. Loosen retaining nut and washer and slide potentiometer out of switch. To install, reverse removal procedure.

Continental Cougar, Mark VII & Thunderbird

Remove lens attaching screw and lens. Remove potentiometer attaching screws. Pull potentiometer assembly and wiring out of the instrument panel. Disconnect wiring connector. To install, reverse removal procedure.