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Adding a factory-type Temp gauge and 3-wire Coolant Temp Sensor...

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    Ok - here's a test. Have you tried to disconnect the green wire from the temp switch and ground it? What happens? Does this illuminate a warning lamp, or does it make the gange pointer move?

    If the gauge pointer moves, then you have a SWITCH installed in place of a SENDER. Probably an error on the part of the parts store employee who looked it up for you.

    If a light illuminates, they you need to search for another green wire in the harness. Does your manual (the one you go to repair the engine) show the wiring diagram for the gauges cluster?


    Ps- Looks like my IP address is now fixed. Above is the repost of the senders picture since the IP changed again.

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      According to the 1990 Ciera 3.3L wiring diagram, your warning light is controlled by the engine ECM. The only green wire under the hood going to a temperature sender should be for a gauge sender.

      I beleive the warning light signal comes from the ECM on terminal F2.

      Try a TU66 sender in place of your existing switch.

      If you ground this wire and the gauge moves, you definately need to install the TU66 sender in place of whatever you have in there now.

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        Okay, a TU66 sender. How will I get a correct connecting plug-in to the switch?
        What is this & what does pulling it out do?