Headlamp: Testing and Inspection
DIAGNOSIS AND TESTINGThe following checks should be performed, in sequence, to determine the cause and correction of trouble and to eliminate unnecessary service work. This unit is transistorized and does not require warm-up time. With the vehicle in a well-lighted area, check the system as follows:
1. Check position of driver sensitivity control knob. If it is rotated to either full counterclockwise or full clockwise position, check with the owner, to ensure operation of the unit is understood.
2. Operate the engine at fast idle.
3. Turn lamp switch on. Set driver sensitivity control knob at approximate center of its rotation. Actual position is dependent on ambient light level.
4. The headlamps should remain on the lower beam in both positions of the dimmer switch when sensor is exposed to sufficient light. If so, proceed to Step 5. If not, perform the following checks:
a. If headlamps remain in the upper beam for both positions of the dimmer switch, remove the hi-low beam relay from its connector. Connect one lead of a test lamp to battery voltage and the other lead to the violet wire of the relay connector. If the test lamp does not light for both positions of the dimmer switch, replace the relay. If the test lamp does light for both positions of the dimmer switch, remove dimmer switch connector. If lamp remains lit, check for a short in the 500 circuit, if not replace the dimmer switch and reconnect the relay.
b Disconnect the sensor-amplifier cable at the in-line connector. The function of the driver control can be fully checked with Rotunda Digital Volt Ohm Meter 007-00001 or equivalent, connected between ground and the white wire (508) terminal. With control fully clockwise, and headlamp on, meter should read approximate battery voltage. In the fully counterclockwise position, the meter should read zero volts. Rotation of control between minimum and maximum sensitivity positions should provide a smooth, continuous voltage change without discontinuities. Replace control if it does not function as described.
c. With headlamps on, the sensor exposed to sufficient light, and dimmer switch in the automatic (high beam) position, disconnect sensor-amplifier cable at the in-line connector. If headlamps return to low beam, replace sensor-amplifier. If not, replace dimmer switch.
5. Place the dimmer switch in the automatic position and actuate partially. The headlamps should switch to the upper beam. If so, proceed to Step 6. If not, perform the following checks:
a. Check for a loose connection at the hi-low beam relay, dimmer switch connector near driver sensitivity control, or in-line connector between the sensor-amplifier cable and the interconnecting wire harness.
b. Check operation of hi-low beam relay.
c. Check for a disconnected circuit (527 red wire) at the dimmer switch.
d. Disconnect the red wire from the dimmer switch connector and ground it to the vehicle body. If the upper beam is obtained, replace the dimmer switch. If not, reconnect the wire and check the continuity of the circuit through the harness to the sensitivity control and sensor-amplifier.
e. Complete continuity of the override circuit can be checked by disconnecting the sensor-amplifier cable from the interconnecting harness at the in-line connector. First rotate driver sensitivity control knob completely clockwise to the maximum range position. Using a test lamp (No.53 bulb), connect one lead to battery voltage and touch the other to the white terminal in the in-line connector. Pull turn signal lever slightly towards driver and the bulb should light. If not, check continuity from the in-line connector to the dimmer switch.
6. Place dimmer switch in the automatic position and tightly cover sensor-amplifier lens with a black cloth. The headlamps should switch to upper beam. If so, remove black cloth and proceed to Step 7. If not, disconnect sensor- amplifier at the in-line connector. Ground the gray with yellow dot wire on the male connector. If headlamps switch to upper beam, replace sensor-amplifier unit. If not, replace dimmer switch.
7. With the headlamps on automatic lower beam, rotate the driver sensitivity control fully counterclockwise. The headlamps Should switch to the upper beam. If so, proceed to Step 8. If not, check the driver sensitivity control for poor connection to ground.
8. If the system responded to Steps 4 through 7 without failure, the unit is functioning properly and all that remains to be checked is the aiming and sensitivity.