What is the three-wire principle of the Jetta radiator thermoswitch?
2 Answers
Jetta radiator thermoswitch three-wire principle is as follows: 1. Line 1 is the positive power supply wiring, which is directly powered by the battery through the No. 1 30A fuse in the fuse box, bypassing the ignition switch. 2. When the temperature reaches 85 degrees, the low-speed terminal No. 2 plug is connected, and when it reaches 93 degrees, the high-speed terminal No. 3 plug is connected, so the thermoswitch does not have a ground wire. 3. The radiator active fan also has three wires: one ground wire, and the other two are the low-speed coil wire and the high-speed coil wire, connected to the No. 2 and No. 3 plugs of the thermoswitch respectively. The function of the thermoswitch on the radiator: 1. The thermoswitch on the radiator is used to control the radiator fan. 2. When the water temperature reaches a certain level, the thermoswitch will control the relay of the radiator fan to close.
As a seasoned mechanic with years of experience, I've encountered numerous issues with the Jetta's coolant temperature switch. The three-wire principle is actually quite simple: it has three connecting wires—one supplies power to the sensor, one provides grounding to complete the circuit, and the third is the signal output wire to the vehicle's control module. The thermal switch relies on internal resistive material to detect water temperature. When the temperature rises, the resistance drops, sending a signal to activate the fan in low or high-speed mode. This design prevents engine overheating or overcooling, improving fuel efficiency. Common problems include aging wiring causing signal interruptions or erratic fan operation. To fix these, check for loose or oxidized connectors. Regularly cleaning the radiator can extend its lifespan, as accumulated dust on the switch may lead to temperature misjudgment. Though small, this component directly impacts engine health. I recommend maintenance every two years to prevent failures.
