Failure phenomenon: an easterly wind (using MITSUBISHI engine) in 2006. Sometimes the instrument shows the high temperature of the coolant and the phenomenon of the instrument pointer to the red line area. Inspection and analysis: first, the basic inspection, the coolant is not short; starting the engine, the original work of the 30min, found that the coolant temperature is not high, and the cooling fan works normally. The reasons for the high temperature of the coolant are as follows: the heat exchanger is not completely opened, the radiator is blocked, the cooling fan is sometimes bad, the cooling solution is blocked, and the coolant pump is not working. It is suspected that the coolant temperature is high at high speed, so the engine is accelerated to the 2000r/min-3000r/min test. The coolant temperature displayed on the dashboard is still normal. Then the road test was carried out, and 5km was not detected. On the road to return to the factory, when driving through a high and low turbulence on the bumpy road, suddenly found the cooling fluid thermometer on the instrument panel pointer to the red line area, the main engraved side open the engine room cover inspection, found that the engine temperature is not high, and the cooling fluid circulation normal. It was suspected that there was a problem with the coolant temperature sensor to the instrument room, but no exception was found after examination. It is doubted that coolant temperature sensors sometimes work poorly. After replacement of the sensor, it is found that the above phenomenon occurs when bumping on the road. Unplug the coolant temperature sensor wire side connector, check the instrument in the cab, and find that the coolant thermometer does not return to the lowest temperature position. When the ignition switch is disconnected, the coolant thermometer pointer is still not moved, and the hand flaps the dashboard. The meter pointer returns to the lowest temperature position. It appears that the coolant thermometer pointer is stuck. Elimination method: replace instrument assembly.