I fixed the temperature gauge on my 1987 Ranger 2.9L. The gauge has never worked since I bought the truck last summer. I confirmed that the fuse was ok so I decided to replace the following parts.
* Temperature Sending Unit
* Temperature Sensor
I don't know which of these parts was the culprit but since I had to remove the thermostat housing in order to reach the sensor and sending unit, I decided to replace the stat while I was in there.
See picture number 3 for the location of the sensors indicated by the red arrows.
The total cost in parts for this project was around $45.00 and it took me around 2 hours to complete cause I did not have a big enough open-end wrench and had to go look for one.
Oh, I also broke the fragile green and red vacum hoses, so I had to buy some tubing and repair the lines.
Arrows indicate the Sending Unit and Sensor.