Why is the air conditioner behind BMW 5 Series not hot?

Vehicle air conditioners are frequently used in winter and summer, especially in cold winter. By turning on the warm air, the interior of the vehicle can be adjusted to a comfortable temperature. Today, let's talk about the problem of insufficient warm air in the car. What happened? Let me briefly talk about the principle of air-conditioning warm air, which is different from air-conditioning refrigeration. Warm air is completed by the heat of engine coolant, that is, the coolant circulated by the engine enters the small water tank in the evaporation box of air conditioner through pipelines, flow valves and circulation valves. After the blower rotates, the air flows to the small water tank, and the air becomes hot when heated, which can be blown out through the air outlet of the air conditioner.

In this process, there will be many electronic and mechanical components such as air outlet sensor, evaporation box temperature sensor, flow valve, circulation valve, water temperature sensor, control unit and so on. If there is no warm air in the car, let's first determine whether the following air conditioning outlets are out of the air and cool. If there is no wind, it may be that the blower is damaged, or the air conditioning filter element is dirty and blocked, or the damper motor is damaged, or the damper baffle is stuck. Another is that there is wind at the outlet, but it is not hot air.

If the warm air is not hot, it is not complicated to judge:

First, let's see if the engine water temperature is normal. If it has been in a low temperature state and does not reach the working temperature, the warm air will certainly not be hot. At this time, we can focus on whether the thermostat has been in a large cycle state, or whether the signal of the water temperature sensor is true, and repair or replace the faulty factory.

Second, we should focus on whether there is a large temperature difference between the inlet and outlet pipes in front of the warm air box. If this happens, the heater box must be blocked and needs to be disassembled, cleaned or replaced.

Thirdly, it depends on whether the flow rate and temperature of coolant entering the heater tank meet the requirements. The temperature can be measured by infrared thermometer, and the flow can be comprehensively judged by the diagnostic data and fault storage of the detector. The common causes are pump loss and damage, and the heater flow valve and coolant circulation valve are damaged.

Fourth, it depends on whether there is air resistance in the coolant system, which is usually not exhausted after replacing the coolant. The special cylinder gasket is damaged. Standard coolant discharge methods can be used for further confirmation.