I don't think a faulty stabilizer would cause the temp gauge behavior you mention.

Both gauges have the same power supply. If they start getting 12 or more volts instead of 10 they start reading high. With a nearly empty tank the gauge would still indicate maybe 1/4 to 1/3 full. And the temp, when cold would read partially warmed up and proceed to max out as it got to operating temp.

But maybe since the temp gauge seems to be having another problem it's not showing this behavior.

Just guessing but maybe there's a fault in the wire from the temp sender and that's what is causing the gauge to read cold sometimes. I've had that happen. When you ground the wire you might jostle the wiring harness and see if the needle bounces. How's the wiring at the firewall connector? Also you could run a wire externally from the temp sensor to the cluster and see what happens.

But if it works right some of the time I think you would see the same behavior as the fuel gauge if it is a bad stabilizer.


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'80 DL 2 door, '89 DL Wagon