Hi Guys I have a 87 fiero with a Pegged out temp gauge. I performed the wire switch in the instrument panel
and temp sensor also replace a new one and still have the temp gauge pegged out at start up and it does
not come back down. whats the next step replace gauge or needle?

The foam around the gauge is prob old, thus the needle sticks in it. Replace it with new stuff and yhe needle just bounces back.

Something went wrong with your temp gauge fix if it still pegs at startup.

we put the needle down and the needle went right back up at start up and stayed there.
Now the temp warning light does come on at start then goes off.

Unplug the temp gauge sensor, free the needle, turn the key to on and see if it stays at zero.

How quickly is your temp gauge pegging out? Check for water in your oil (look for moisture on the oil cap or milkey brown oil), allso look for oil in your coolant.

Keep talking ...I have the EXACT same issue...

Pegs hot...normal temp at housing with infrared thermometer

Idiot light lights up at approximately the time it reaching normal running temperature.

I did the wire switch...I was afraid I had messed up...

Keep talking about the gauge issue..I am unclear about the repair issue that was discussed in this thread.

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86 5 speed 2.5 Iron Duke
Notchback.

The problem the OP is having may or may not be related to the 'temp gauge fix' to correct a GM wiring mistake, but this thread is called Pegging Temp Gauge so there should be a link to the document to fix that. If that fix is done incorrectly or half way, it may explain some of what is going on.

Temperature Gauge Repair

[This message has been edited by Gall757 (edited 12-12-2016).]

we tried placing temp gauge down and disconnected temp sensor and started the car and the temp gauge
stayed around 100 degrees as soon as we plugged back the temp sensor it slowly pegged back up and never back down.
Any tried replacing the temp gauge?

The position of the needle on the temperature gauge shows the resistance of the element in the temperature sensor. In other words, the gauge is an Ohmmeter. The gauge is supposed to read 100 degrees F when the sensor resistance is 1365 Ohms and 260 degrees F when the sensor resistance is 55 Ohms. To test the gauge for accuracy, pull the plug at the sensor, stick one end of a resistor in the plug and ground the other end of the resistor to the car. Turn the ignition to "On". If you don't get any readings, try the other location on the connector. Assuming the test resistor is near one of the values mentioned above, your gauge should be in the general vicinity of either 100 or 260 degrees F. If not, the needle has probably shifted. Test with both resistors to determine the gauge reads about right at both ends of the scale.

That is from the link in the above post... try this it will tell you if the guage works or not and you can set it pretty close. Then see if it still pegs high. If it does replace the temp sensor.