So I have a 1995 Ranger extended cab 4x4 with the 4.0L engine. Truck only has 50,000 original miles. Truck sat for years. I ended up having to do head gaskets from where it sat so long. That was about 10,000 miles ago. Now my problem is my temperature gauge is all over the place. It never gets above normal operating temperature. But it will swing from normal to cold and back the whole time you are driving. I have replaced the thermostat twice, sending unit three times. It has a new radiator. I have also flushed the whole system and the heater core multiple times. I am at a loss.

 

Frayed insulation causing shorting out?
Broken wire within a plug?
What attaches to the sending unit...a bladed connector or a "push-on to a threaded stud?
Did you buy a succession of 3 no-name sending units?