Auto lighting on 1998 Ford Explorer quit working

My headlights on my 1998 Ford Explorer use to come on automatically by a sensor on the rearview mirror, then all the sudden they started flashing off and on and then it quite working and I have to turn them on manually, which sucks if you so use to them coming on all by themselves. Can someone help me with what the problem is. My Haynes Repair Manual doesn't have any listings for this problem.

don't take this wrong but you do have the slider bar on the mirror set to on, right

Yes. I've even slid it from one side to the other and it didn't make a difference.

Is it just your headlights that don't come on or is it all your exterior lights? I'll send you a wiring diagram that may help. I'll help you through it if need be.

there is a 5 wire connector on mirror; connector disconnected, ignition on,shift lever in reverse,three should have 12v, 1 is ground, the last grounds the relays for lights to come on, check with test light for the 12v and to activate relays

I can turn the lights on by the switch but the sensor should turn them on automatically once it gets dark

White/purple and light green/ yellow should be hot all the time. Red / yellow should be hot in start or run. Red/yellow is fed from I/P fuse panel fuse #11. Light green/ yellow is fed from I/P Fuse panel Fuse # 30. White/purple is fed through Park lamp relay and then to Power distribution box fuse # 11. Black is ground and black/pink goes to auto Day/night Mirrors. Hope it helps

Ok, thanks, I'll have it tested tomorrow. Just a thought....my friend kind of wondered if it's the sensor on the mirror that might have went out....is that possible?

Check for 12 volts on those wires(remember one only has 12 volts if the car is running, the other 2 at all times.) if you have voltage on all three and your ground is a good clean ground, then it is safe to say your sensor is bad.

Ok thank you very much!!!!

ok I did what was suggested and found out that the white/purple wire is only reading at 1.5 volts. We can't find the Park Lamp Relay box (not the fuses, we found all 3 of those), does anyone know where it might be located???

the wh/purple wire is a ground for the park and headlamp relays. ground the wire to see if the lights work

The park lamp relay,dimmer relay and headlamp relay can be found behind the dash just below the heater-a/c controls.