The unit is connected directly to the fuel injection control unit and to the temperature sensing
switch unit which controls the fan motor and the coolant overheat warning lamp. If it is thought to be faulty it can be
tested only by substitution.
Temperature sensing switch unit
This unit controls the coolant overheat warning lamp and the fan motor. It is mounted by one or two
screws in the electrical components box underneath the rear of the fuel tank. If thought to be faulty it can be tested only by substitution
Coolant overheat warning lamp
This is merely a bulb which is renewed if faulty as described in Chapter 10 - Electrical.
However, if it should light when the engine is still cold, the fault is most probably due to a poor earth connection between the engine and frame.
Clean the bellhousing/frame mounting point as described in
Chapter 1, Section 36 - Refitting the engine unit to the frame,
also the frame earth point behind the steering head. Both must be cleaned back until metal-to-metal contact is restored to
ensure a good earth; apply a thin coat of silicone grease to prevent corrosion and tighten the mounting bolts securely.
11.2 Coolant temperature sensor is mounted in coolant pipe stub
11.4 Temperature-sensing switch unit is mounted in electrical components box