Question: I bought a used 2000 Escalade, and the temperature gauge didn't work well from day one. The dial falls well below the 100-degree mark and goes up to only about 150 or 160 degrees when driving. This is the only gauge in the cluster that isn't working right. I've had the water temperature checked for fear that it was getting hot without my knowing, but the temperature was fine. I checked the thermostat housing ground on suggestion from a mechanic and I've changed the antifreeze. What should I do next?
| 2000 Cadillac Escalade front View
Answer: Noticing all other gauges working properly was a good observation. All the gauges use a common power source, so we can safely eliminate the lack of a full 12 volts at the instrument cluster as being an issue. The majority of the time, a condition like this turns out to be a defective coolant temperature switch (sensor) or a poor electrical connection. The temperature sensor has a one-wire connection and is located near the thermostat housing. Of course, you want to be sure the connection is clean and tight. Perhaps have a friend observe the gauge for fluctuations (ignition on) while you jiggle the connection. The fact that the gauge's needle dips well below the 100-degree mark has me suspecting the gauge itself. If the sensor looks good, the next time the engine is cold and the gauge's needle is way down low, give the dash a good shot with your fist (don't break anything) and see if the needle pops back up. If it does, it's either a bad gauge or a bad connection inside or behind the instrument cluster. Other than that, proper gauge diagnostics is recommended. This requires a special tool, which uses a variable resistor to simulate the resistance change of the sensor as coolant temperature increases. If you connect the tool at the sensor and the gauge reads correctly, then the sensor is bad. If the gauge still reads incorrectly with the correct signal from the tool, you have to work your way up to the cluster to determine if it's a fault in the wiring or the instrument panel. Typically the entire cluster will be replaced if the gauge is found to be at fault.
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