We have a 2012 CAT 299C (VIN: CAT299CCJSP02002) that's showing an issue with coolant temperature readings. After running for about 3 minutes, the temp gauge spikes and the machine reports it's overheating. However, once you stop moving, the temp drops back down to about 2/3 on the gauge. We've already replaced both the thermostat and the coolant temperature sensor, but the issue persists. We also verified the actual temperature using an infrared gun, and the engine wasn’t even fully up to operating temperature when the spike occurred. As a test, I ran a new wires directly from the ECU to the temp sensor, and that completely resolved the issue — confirming it’s a wiring problem. I’d really like to fix the original harness properly rather than rely on a bypass. My question is: Has anyone experienced similar issues with this model, specifically wiring faults in the harness related to the temp sensor? If so, where in the harness did you find the problem? Any input would be appreciated.
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