temperature light, 81 imperial. Frank thinks he has a fever.

[lastws6]

So.. My temp warning light came on the other day. Right after I cleaned pretty thoroughly under the hood. Yeah, I know.. not the best idea. The temp seems low enough, no crazy boil over when opening the cap at all.. everything seems normal, except for the light. Since, I did a thermostat change, full coolant flush, and even took the temp sensor out of a spare factory 4bbl intake I had and swapped that out. Light still comes on as soon as the motor just gets up to temp.. I swear it isn't running hot at all.

So what gives?