Kingy said:

Anyway, I’ve just got home from work. Spent most of the day today, and nearly all of yesterday trying to diagnose and repair an electrical fault in one of the trucks that meant I had no headlights. The park lights worked, but no go on low beam, or high beam.

Bypassed all safety systems and hotwired the headlights, they work fine. Checked all fuses, replaced them anyway, no difference. Replaced solenoids, no difference. Called the sparky, he spent several hours on it. No luck.

Eventually, I had to move the truck to unhook the trailer, I noticed that the lights are working, wtf?

Turned the truck off, lights went out. wtf? It never used to do that. Occasionally I would accidentally leave the lights on in daylight, pull the keys out, lock the truck and drive home. Half an hour later, someone would ring me to tell me that the headlights are still on in the truck and I would have to drive back out there to unlock the truck and turn them off.

Now the lights won’t work unless the ignition is on, and nothing has changed on the truck. No work has been done on it, it just decided randomly to mess with me. Bastard thing.

Call a priest.