Headlights stay on?

WALLYONEWORM

MEMBER
1998 FORD F-150

When this year truck is started, the headlights come on automatically. As of last week, when I shut the truck off, the lights stay on, and I have to disconnect battery in oreder to get them off. When I reconnect battery to start again, the lights come on again. They seem to be stuck on. This does not seem to have anything to do with the switch, as it happened during the day when only the "automatic" lights were on. It happened during a cold weather snap if that is any help. What should I replace to get these lights back to normal (coming on when started, shutting off when engine is shut off) ?

1 Reply

DAVE H

MECHANIC
13,384 POSTS

TEST B: AUTOLAMPS ALWAYS ON
Verify Condition - Turn ignition off. Ensure autolamp time delay switch is in OFF position. Ensure headlight switch is off. If headlights are on, go to TEST C: AUTOLAMP TIME DELAY INOPERATIVE. If headlights are off, go to next step.
Check For Short To Ground - Disconnect light sensor amplifier located in center of instrument panel under instrument panel relay cover. If headlights turn off, replace light sensor amplifier. If headlights do not turn off, go to next step. Recheck system operation.
Check Headlight Relay - Remove autolamp headlight relay from relay box. Relay box is located in center of instrument panel under instrument panel relay cover. Measure resistance between relay terminals No. 3 and 5. See Fig. 6. If resistance is more than 10 k/ohms, repair Light Green/Yellow wire circuit. If resistance is 10 k/ohms or less, replace relay. Recheck system operation.
TEST C: AUTOLAMP TIME DELAY INOPERATIVE
Check Fuse - Check fuse No. 29 in instrument panel fuse box. If fuse is okay, go to next step. If fuse is blown, replace fuse and recheck system operation. If fuse blows again, locate and repair short to ground as necessary.
Check Voltage To Light Sensor Amplifier - Disconnect autolamp light sensor amplifier located in center of instrument panel under instrument panel relay cover. Turn ignition on. Measure voltage between ground and terminal No. 1 (Red/Yellow wire) at light sensor amplifier wiring harness connector. See Fig. 1. If battery voltage is present, go to next step. If battery voltage is not present, repair open Red/Yellow wire between fuse box and light sensor amplifier. Recheck system operation.
Check Autolamp Time Delay Switch - Turn ignition off. Disconnect headlight switch connectors. Rotate autolamp time delay switch thumb wheel to MAX position. Measure resistance between headlight switch terminals. See Fig. 2. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, replace headlight switch and recheck system operation.
Check Ground Circuit - Measure resistance between ground and terminal No. 1 (Black wire) at headlight switch 6-pin Black connector. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open in Black wire ground circuit. Recheck system operation.
Check For Open In Circuit No. 220 - Measure resistance of Purple/Orange wire between terminal No. 2 at headlight switch C244 wiring harness connector and terminal No. 2 at light sensor amplifier wiring harness connector. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open Purple/Orange wire. Recheck system operation.
Check Autolamp Time Delay Switch Resistance - Measure resistance between terminals No. 2 and 3 at headlight switch while rotating autolamp time delay thumb wheel from MAX to OFF. See Fig. 3. Resistance should vary from 3.3 k/ohms to 225 k/ ohms. If resistance is as specified, go to next step. If resistance is not as specified, replace headlight switch assembly.
Check For Open In Circuit No. 217 - Measure resistance of Dark Blue/Orange wire between terminal No. 3 at headlight switch C244 wiring harness connector and terminal No. 5 at light sensor amplifier wiring harness connector. See Fig. 1 and Fig. 4. If resistance is 5 ohms or less, go to next step. If resistance is more than 5 ohms, repair open Dark Blue/Orange wire. Recheck system operation.