What is the reason why the back heater of BMW 525 is not hot?

The back heater of BMW 525 is not hot, which is divided into two reasons: the engine cooling system is faulty or the heater control mechanism is not working well. During maintenance, it is necessary to determine the reason and then carry out corresponding maintenance. The following is a detailed explanation: refrigeration system problem: the thermostat is always on or the thermostat is turned on too early, which leads to the premature circulation of the refrigeration system and the low external temperature. Especially when the car is running, the cold air quickly cools the antifreeze, and the engine water temperature is not high, which leads to the failure of the car warm air. The impeller of the water pump is damaged or lost, which makes the flow through the small warm air tank insufficient and cannot increase the heat. There is air resistance in the engine cooling system, which leads to poor circulation of the cooling system, resulting in high water temperature and lukewarm air. If there is air in the cooling system all the time, it is likely that the cylinder pad is damaged and gas leaks into the cooling system. If the inlet pipe temperature of the small warm air tank is high and the outlet pipe temperature is low, this situation should be that the small warm air tank is blocked and should be replaced. The problem of heating control mechanism: the warm air of the car uses a blower to blow heat from a small heating tank to the cab. If the air volume is insufficient or the distribution of cold and hot air is not good, the temperature of the warm air will be low. Check whether the filter is dirty or blocked, clean it and replace it in time if necessary. Check the operation of the blower gear to ensure that the gear reaches sufficient speed. If the knob is set to the warm air position, the air volume is large enough, the wind direction is normal, and the cold air blows out, check whether the cold and hot air control flap cable in the warm air box falls off, whether the warm air impeller is damaged, whether the flap falls off, etc. After troubleshooting, the warm air temperature will rise.