Combines need help low coolant warning light

This is an M3 gleaner

this is not a switch , it is simply a ground probe. Take the wire off and ground it, if the light goes off the water is perfect ph 0 rare almost impossible or the probe is broke, or if it does not go out, then the sender wire is broke or out of one of the pin couplers.

Thanks. Found that the post on radiator was croded so not making contact. Dean