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Message: [QUOTE="markfuga, post: 895187, member: 10964"] It’s a little too cold outside so I brought some of the project inside. Calibrating the temperature gauge is now checked off the list. Unfortunately it wasn’t as easy as it could have been because the correct temp sensor is a ½ NPT and the 7.3 uses a 3/8 NPT. I didn’t want to fool around with couplers and adapters so I searched for an equivalent 3/8 NPT sensor. I spent many hours surfing the web (mostly Corvette sites came up in my searches) and found a close matched sensor (Wells TU66) which reads about 100 ohms higher throughout its range than the gauge is calibrated for. The fix is to add a resistor in parallel with the sensor, but figuring out the resistor size is the challenge. I cheated, went to Radio Shack and picked up a 1K ohm potentiometer. I wired it in parallel with the sensor, wired everything up to the battery and brought the pot of water to a boil (212 degrees). When the water was at a boil I adjusted the potentiometer until the needle on the gauge was just past the “halfway” point. I then read the potentiometer and determined a 470 ohm resistor was needed. I went back to Radio Shack, bought the resistor, attached it to the back of the gauge and ran the test again. The needle came off “cold” at 140 degrees and swept smoothly as the water came to a boil and landed just past the hallway point again. The needle was straight up/down in the center of the sweep at 200 degrees which should be normal operating temperature (I have the 203* thermostat). [/QUOTE]

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