Audi A4 idle heater is not hot.

It's easy to happen to an old car like you. We have also encountered suggestions that you should replace the small heater water tank. Although it is not blocked, the throughput is reduced and the heat exchange capacity is also reduced. This problem can be solved by the following steps:

1, first determine the fault, the engine temperature reaches 90 degrees, turn on the warm air to raise the temperature, and make sure that the air blown out of the air outlet is cold. Open the front cover of the engine, find the air inlet pipe of the heater tank, and touch the two water pipes with your hands, indicating that the heater tank is not circulating. The car is equipped with a warm air control solenoid valve at the lower part of the front windshield, as shown in the figure below.

2. According to the control principle of warm air, it is determined that the two solenoid valves are not open and are in a closed state, so the control voltage of the solenoid valves is further measured with a multimeter.

3. With the adjustment of temperature, the voltage of the solenoid valve also changes, indicating that there is no problem with the control, which should be the problem of the solenoid valve. If the solenoid valve is further decomposed, we will understand the reason.

4. Replace the heater control solenoid valve with a new one, and the problem is solved.