I had this light come on briefly yesterday. Dew indicator? I don't think so. But, I don't know why this would be coming on in our vehicles. After a little research, I found that this light is used on diesel engines to indicate that a resevoir which collects moisture from from the fuel is full and needs to be drained. Since they don't make diesel explorers, I don't know why this light is coming on. I was parked on an incline, at the time, and the light was on when I started the truck. As I pulled off the rocks onto the street, the light flickered and then went out. It hasn't come back on yet, so I'll just hope it stays off. For reference, my truck is a 98 4x4 sport. It has the original cluster that has never been messed with.