What Causes the Temperature Warning Light to Illuminate When the Coolant Temperature is Normal?
2 Answers
The temperature gauge shows normal readings but the red warning light is on, which is generally a false alarm from the coolant temperature warning system. When the owner adds antifreeze, if the vent hole on the side of the reservoir's damping tube is positioned too low, it can create a compressed air column inside the damping tube. This causes the liquid level in the damping tube to be significantly lower than that in the expansion tank and close to the sensor's alarm threshold. Vibration during driving can easily trigger a false alarm. Below is an introduction to the temperature gauge: 1. Normal coolant temperature: The coolant temperature typically displays between 70-90°C after the engine warms up, which is considered normal. If the coolant level in the radiator is low, the temperature will rise, requiring the addition of water. If the temperature gauge needle approaches the 'H' mark or the red danger zone, and the temperature warning light comes on, it indicates that the engine coolant temperature is excessively high. 2. Working principle: The temperature gauge sensor is a thermistor-type sensor threaded into the engine's coolant passage. The thermistor determines the current flowing through the temperature gauge coil, which drives the needle on the gauge to move accordingly.
The coolant temperature light is on but the temperature is normal. I've encountered similar situations while driving, which can be quite confusing. The most common cause is a faulty coolant temperature sensor. It detects the temperature and sends signals to the dashboard. If the sensor is broken or clogged with dirt, it may incorrectly trigger the warning light. Sometimes, poor electrical connections or short circuits can also cause false alarms from the system. Additionally, dashboard malfunctions, such as aging instrument modules or software bugs, can lead to false warnings. I recommend not worrying too much, but it's essential to get it checked promptly to prevent minor issues from escalating. You can start by inspecting the sensor connections in the engine bay for looseness or oxidation. If that doesn't help, visit a repair shop for professional diagnostics. Regular maintenance, including having a technician clean the sensor, can help prevent such issues.
