What are the symptoms of a faulty coolant temperature sensor in an old Jetta?
2 Answers
Symptoms include the temperature gauge needle not moving and pointing to the highest position; difficulty starting when the engine is cold, displaying a hot engine temperature signal; increased fuel consumption, unstable idle; difficulty accelerating, with the engine speed not increasing even when the throttle is fully pressed. Below is more information about the automotive coolant temperature sensor: Introduction: The water level sensor inside the container transmits the sensed water level signal to the controller. The computer inside the controller compares the actual water level signal with the set signal, calculates the deviation, and then issues "open" or "close" commands to the water supply electric valve based on the nature of the deviation, ensuring the container reaches the set water level. After the water intake process is completed, the computer in the temperature control section sends an "open" command to the electric valve supplying the heating medium, and the system begins heating the water inside the container. When the set temperature is reached, the controller issues a command to close the valve, cutting off the heat source, and the system enters a heat preservation state. During the programming process, the system ensures that the electric regulating valve controlling the heat source does not open unless the safe water level is reached, thereby avoiding heat loss and accidents. Function: Converts the coolant temperature into an electrical signal.
I drove an old Jetta for several years, and once the coolant temperature sensor failed. The temperature gauge seemed stuck, always showing low readings while the engine was actually scorching hot. The cooling fan refused to turn on, nearly causing the engine to overheat on the highway – I got quite a scare when smoke started pouring from under the hood. During startup, the car jerked violently, and idle speed fluctuated erratically because the faulty sensor misled the ECU into misjudging the temperature, resulting in incorrect fuel injection and unnecessary fuel consumption. Long-term neglect could damage the cylinder head or cooling system, with repair costs running into thousands. My advice: pay close attention to your dashboard while driving. If anything seems off, pull over immediately to check the coolant level – don't push your luck. A simple diagnostic and part replacement at a repair shop should cost just a few hundred bucks.
