Changing the AC between Fahrenheit and Celsius

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Thanks to Joshua Teixeira :

In my 95, there is a red wire that is grounded out under the dash, just to the left of the floor console. Grounding this wire makes the ETAC show temperature measurements in C, and in my Canadian car, it came this way from the factory. Apparently, in American cars, this wire is not grounded, but is taped to a wiring harness in the general area. Some have installed a switch to ground this wire to be able to switch the display from F to C.

While I had the dash apart in the 89, I figured that I would simply find this wire and ground it out, since the ETAC shows F, even though the car is Canadian and has a metric dash. Well .... I removed everything in the dash, speedo, ETAC, radio, even the passenger vents (and cleaned years of dust from the interior temperature sensor BTW). There was no trace of any red wire to be found after a couple of hours of looking. I even checked all the wires coming from the ETAC, and none was pure red, i.e. red with no stripe, as I had seen in my 95.

Since I don't have a copy of the electrical schematics for the 89, (yet) I called Scott McNamee, a fellow Canadian. Sure enough, he was able to find the pin-outs for the ETAC, and one of the pins was shown for switching the ETAC from F to C. (I figured this had to be BTW, since my parent's pre 89 sables with the digital dash had the same ETAC, the display did switch back and forth with the digital dash). Scott told me it was pin 20, so I looked at the ETAC, where the pins are numbered (actually the numbers span the two connectors, as if it were one long connector instead of two narrow ones), and then at the corresponding connector, and lo and behold, there wasn't even a wire in that pin-out. I shoved a wire in the hole in the connector where the wire should have been, grounded it, and viola! The display switched to C. I thanked Scott for his assistance, and connected the wire to a spare switch the previous owner had left in the dash, so I could switch the display back and forth. The previous owner had actually glued a temperature conversion chart to the dash beside the ETAC! :-)