On 18 Feb , 2017, at 6:20 PM, Jim Felder wrote:

> coolant cap/valve is essentially blocked 

        That could be Part of the problem since any Air or Other Gases in the System are meant to Collect & Escape

there ~ If that Escape Route is Blocked & Enough Gases collect, the Coolant Level will be Forced Down & when It's

down far enough the Light will come on ~

        The ability to turn the Light Off with a Jumper leaves only the Coolant Level or Sensor Itself as the Culprit ~

Since We Know that the Circuit Ahead of the Connector is Good & If We Are Absolutely Certain That the Bottle Is 

Always Full >> The Culprit Has To Be The Sensor ~ It Either has a Bad Connector or it is Dirty ~

                                                                                        ORR ~ DeanB