My headlights started flashing on my f150 2001 SuperCrew the other day. This only happens when the ignition switch and headlamp switches are off. The headlights and taillights intermittently come on, sometimes blink a bit, and then go off. This continues to occur while the truck is sitting parked with the ignition and headlamp switches off.

Strangely with the ignition off and the switch on auto, the lights don't blink - they stay off as they are supposed to.

So my questions are:
#1 Anyone have the wiring diagram for the headlamps for a 2001 super crew f150? I think the auto lamps are likely on a separate page than the headlamps and I would need that info too.

#2 Anyone have any ideas what's going on?

Thanks.

 

Is the truck equipped with DRL?

 

What trim level is the truck ?
- XL, XLT, Lariat, FX4, etc.

Do you have the Factory RKE ( Remote Keyless Entry ) or an aftermarket keyless entry / remote start ?

From the diagram question, are you leaving the main headlamp switch in the autolamp position ?
- If so, does it do it when the main headlamp switch is in the off position ?

I seem to recall my 2001 with the factory RKE, when it was locked the headlamps & parking lamps flashed, that is why I asked about the RKE or aftermarket install.

The diagrams

 

It does have DRLs and is Lariat trim level. It is equipped with factory RKE. Has no aftermarket alarm or anything that would affect the headlights.

EDIT - let me change that DRL comment - It has fog lamps in the bumper. I'll need to look again on the DRLs.

The problem only shows up when I put the headlamp switch in the OFF position. Then the lights blink randomly. If I put the headlamp switch in Auto - it shuts them off and leaves them off.

Edit - Random weirdness -I'll verify further but I swear light on the front of the truck triggers the flashing behavior. I'll look more tonight.

 

Based on your drawings - it would seem the common point is the autolamp module. I would guess if I pull the connector off the autolamp module and the problem goes away then it is either the ignition switch or the autolamp module. The security module would seem out of the loop since it doesn't know anything about the headlamp switch.
Any other ideas appreciated?

 

No DRLs. Just pulled off the dash cover to look at the autolamp and if there was a DRL relay. No DRL relay.
Starting flashing like mad while messing in that area. Would seem like a short but don't see anything obvious. - Will report back if I figure out anything else.

 

Pulled the autolamp module - lights do work correctly now with the switch in the off or on position.

I noticed a little weirdness though - I measured the voltage with the autolamp disconnected at the auto terminal (pin 4) on the autolamp connector. It read 12 volts when auto was on and 10 or so with auto off and the key off. I put a resistor between this terminal and ground and the voltage went to zero-ish. That seems weird. My guess is that the headlamp switch isn't quite right.

 

I'm at the point where I need to test the headlight switch to isolate whether the autolamp module or the headlamp switch is causing the problem. Does anyone have the headlight switch test page from the wiring diagrams?
Again my truck is a 2001 f150 supercrew, Lariat without DRLs. It has fog lamps.

 

 

Using a cheap ohmmeter I checked continuity between power and autolamps with the switch off. This should be open. It was on my cheapo meter. Since it still seemed like there had to be some connection between the two points, i hooked up a power supply to the power input and measured the voltage on the autolamp output when the switch was off. 10.6 volts.
I then got out a Fluke meter with a 20 meg resistance scale. Measured 3.8 Meg - should be open.
Looks like the headlamp switch is bad. Very weird..

Sscully - Thanks for all the drawings. Very helpful.

 

Replaced the headlight switch with a Motorcraft OEM from Amazon. No more flashing when the switch is off. Lights are fixed.