I have a 89 with the 4.2 engine. I have been trying to figure out how to fix the temp gauge and I now have a couple of questions.
When you look up the parts online, you get a coolant temp sending unit that screws into what I think is the thermostat housing. This screws in and has two wires coming out with a connector. You also have the other temp sensor that is smaller and goes closer to the fire wall, it has only one wire going to it. I have both of these. I tried grounding the smaller sender wire to see if the gauge moves and nothing happens. But I also checked the other sending unit with the 2 wires and neither side has power going to it. Before I assume that the gauge is bad, shouldn't the 2 wire sending unit (which I think has to do with the computer, but I could be wrong?) have power going to at least one side? Is there maybe a relay controling all this? I am just out of ideas what to try next. Any thought would be appreciated.