I just bought a 1998 mustang gt from an auction and it has a few problems. The radiator fan was wire up to a switch because connection plug to the fan was melted and the heat gauge does not work.So I bought a new plug and wired it in and replaced both sending units. The fan will come on when the ac and heater is on but not by it self when it gets hot it won't and the temperature gauge still dont work. I can take the connector off the heat sending unit an the fan will come on but as soon as I put it back on it shuts off. What's next?