If I were you, I'd try unplugging the sensor. The auto function should default to always on (just a guess, maybe it will throw a code too). Then you could drive around and see if the problem occurs. If it does, then it's something with the switch. If it doesn't, then it's something with the sensor, it's connection, grounding or reading circuit (BCM?). Just my two cents, unless someone has a better idea.

 

Yes, Raphael, that makes sense. I disconnected the sensor, and the lights do stay on. I'll drive it like that for a while, but not at night, and see if the headlights stay on. I should know by the little headlamp light on the dashboard. Thanks for the idea.

 

Nope, not the sensor. The lights still go off even with the sensor removed. Also I noticed that the brightness of the dashboard lights sometimes flickers. I'll bet it's related. I'll keep plugging away at the problem and posting the progress, and, with some luck, the solution.

 

Hello! Did you ever fix the autolamp sunload sensor issue with your Fiesta? I'm having the same problem with it cutting off intermittently at night and the dashlights randomly changing brightness. On that note as well, how did you remove the sensor? I can't find any documentation online.

 

No, I haven't figured it out, but I know it's not the sensor, so don't bother removing it. I believe instead that it's an intermittent ground, but haven't yet proven it. In any case, I don't remember having trouble removing the sensor. To be precise, I popped it out and popped it in plenty of times trying to diagnose the problem. I just pried it out with a pocket knife. There are two little tabs that hold it in, but not tightly. What I experienced, and what you should also experience, if you remove the sensor, is that the dashboard lights continue to randomly change brightness. If it were sensor-related, the lights would remain constant. I am certain this rules out the sensor.