Fault diagnosis: Technicians use special diagnostic equipment to detect that there is a current fault code of "heating power is too low" in the KLA automatic air conditioning control unit, but after clearing the fault code, the fault code no longer appears.
Read the actual value of the temperature sensor data. The left air outlet temperature is 20.6℃, the right air outlet temperature is 20.4℃, the internal temperature is 20.0℃, and the external temperature is 8.0℃ ... From the above reading, it is obvious that there is insufficient heating.
Read the CAN data in the actual value. The engine speed is 6 17r/min, the engine water temperature is 91c, the requirement of the water pump is "on", and the state of the water pump is "on". The data is all right, and no fault is found.
Working principle of automobile heating system. When the engine is working, the coolant is heated in the engine cylinder, enters the warm air box through the water inlet pipe under the action of the water pump of the cooling system, and sends the heat emitted by the coolant to the car or the windshield through the blower, thus increasing the temperature inside the car and defrosting. The cooling liquid emitted from the warm air water tank is pumped back by the water pump through the return pipe to realize warm air heating.
According to the working principle of heating system, the reasons for the failure are: 1 thermostat failure, which often turns on or turns on too early, resulting in low water temperature; 2 pump failure, impeller damage or loss of rotation, too little coolant flowing through the warm air box; 3 there is air in the cooling system, which leads to poor circulation; 4 air conditioning water valve failure, can not be opened normally, too little coolant flows into the warm air box; 5 heater water tank is blocked; 6 control system failure, etc.
Read the actual value of engine temperature, the temperature is normal, and eliminate the fault of low coolant temperature caused by thermostat.
Because the engine is not hot at idle speed, only warm air is hot at high speed, it is suspected that there is a problem with the water pump in the cooling system, and no fault is found after removing the water pump for inspection.
Replace the air conditioning water valve, and the fault still exists.
The structure of the warm air water tank is actually a miniature version of the radiator of the engine water tank, and there are many small cooling pipes in it, which are as easy to block as the radiator of the water tank. After the inside of the warm air water tank is blocked, the coolant flowing through it slows down, the flow rate decreases, the heat is insufficient, and the warm air is not hot. Because the workbench needs to be removed to replace the heater tank, the workload is very heavy, so the water pipe of the heater tank of the original car is disconnected, and a heater tank is connected outside the car to dissipate heat with a blower. When the engine is idling, the air is not hot and the fault still exists.
(Photo/Text/Photo: Pacific Auto Network Q&A called Beast)