Hey guys, having an issue with the coolant gauge in my '86. When I first start the car, the gauge reading normal, but within a 1/4 mile of normal driving it's sitting past the L of NORMAL, almost all the way to the top. I've verified the car is running at normal temp, hovering around 200, give or take a few degrees. How can I get my gauge closer? I know they aren't the most accurate, but this is way too far. I'm tested it a couple different ways, but I'm running out of ideas. I grounded the sensor wire, and it shot up even higher until removed. Combined with the fact that it works normally the first minute, I doubt i have a short. I've replaced the sending unit twice, both with quality units, no change. The oil pressure and fuel gauge work as expected, so I don't think it's the instrument voltage regulator. I verified all the ground wires, and even put a jumper cable from the engine to the battery to eliminate a grounding issue.
Is there any way to test the gauge? I saw on a couple boards for different vehicles where they wired in a potentiometer to adjust the resistance of the sending unit, but that seems kinda hacky. Any thoughts?
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