Sym Fiddle III 50 - Engine Temperature Sensor Illustration and Testing

SYM 4
. ELECTRONICALLY CONTROLLED CARBURETOR SYSTEM
4-9
Engine temperature Sensor Illustration:
Basic Principle
Cylinder head temperature sensor is an NTC thermistor chip, its resistance changes with temperature
changes, so can the acquisition cylinder head temperature in real time.
Function description:
● Use of ECU provide DC 5 v power supply, a total of two pin plug, 1 branch voltage output pin; 1 for the
grounding pin.
● Its main composition is a negative temperature coefficient thermistor (smaller temperature rise of
resistance).
● Device in the cylinder head, along with the engine temperature sensor resistance, with the induction to
the temperature change, and converted into a voltage signal is sent to the ECU to calculate the time of
the engine temperature, ECU again in accordance with the state of engine warming-up correction repair
time and ignition Angle.
Testing Procedures:
● Resistance measurement:
● Remove the engine temperature sensor.
● Use "Multi-meter" ohms range, inspect the sensor resistance.
Detection judge:
The relationship between Resistance value and temperature：
Temperature(℃) Resistance value(KΩ)
-20
969.8±48.5
20
127.6±6.375
40
54.9±2.745
80
13.01±0.65
Treatment of abnormal phenomena:
● The engine temperature sensor is damage, or adapter connector poor contact.
● Check whether there is any abnormal on main distribution line.
● When the engine temperature sensor is abnormal, suggestion is to replace new engine temperature
sensor.
ET SENSOR
TPS
O
2
SENSOR
IGN COIL
ACG/FLY
WHEEL
PLUG
CPS
ECU
BATTERY