just dumped in some diesel fuel supplement/anti-gel napa brand and now my water in fuel light is on and will not go out (well its still got that fuel in it) but there is no water in the fuel and the separator was drained more than 4 times. any ideas? thanks

 

I'd go ahead and replace the filter and see if the light goes out.

 

check the wire to the filter head to see if it is shorting out against the engine or if the insulation is compromised.
i have not had a water in fuel sensor on my truck in over 25 years.