While the truck is on, but the headlights are off, the headlights flash. Once the headlights are turned on, they work normally. I thought maybe it was the headlight switch, but I removed it and the headlights kept flashing. Any ideas?

 

Does it have an aftermarket remote keyless entry or security system? Maybe a goofy factory system.

Sixto
93 E150 Chateau 5.8 191K miles

 

There is a headlight module that controls the DRL's. It keeps them on dim when key is on, then goes to regular bright when you pull the headlight switch on.

The replacement module is under $60 at Rockauto. I didn't want to spend that money when my headlights were flashing, so I just unplugged it. Now I have regular headlight operation with no DRL.

The module is under the plastic cover that is atop the radiator top.