[Peter Serio]

There was a big change in the wire windings on that temperature gauge from the year 1978 to 1979. From the front of the gauge you can't tell. But '79 and up takes a different temperature gauge sender.

Just FYI: those old GM gauges will loose their calibration after about 20-25 years. I have the original printed chart that came with a Kent Moore tester I bought. I could post a close-up of the chart if there is any interest. It gives specifications (in ohms resistance) for values that correlate to lines on the dial face. The chart gives you 3 "test" points on each dial: the start position; in this case that line is marked 100 degrees. Your 1/2 way line and your max overheat line. Given the age of the car I would get out some fixed resistors, that or a decade ohms resistance box, and check the gauge first. Replacing senders, and guessing on which one to try is not really the best way to go about solving this problem. I wonder, would the aftermarket even know, today, that a 1978 & prior Trans Am temp gauge sender is not the same as the 1979 & up sender?


I fully agree with statement above that modern aftermarket (replacement) senders are not made to the same quality and accuracy standards as would be the original GM sender.

Another thing to keep in mind would be the printed circuit on the back of the gauge housing. Those can go bad over time and at the 42 year mark that is something that might need replaced, if anything just for peace of mind. The touch points from the copper footprint(s) to the Silver 6-32 nuts on that back of the cluster sometimes corrode &/or rust and those affected should all be taken apart and cleaned (&/or replaced) with new fasteners.