In-Vehicle Humidity Auto Idle Stop Conditions

Auto idle stop is disabled when the climate control unit anticipates windshield fogging. The threshold depends on outside air temperature, the in-vehicle temperature, and the in-vehicle humidity. To determine the approximate auto idle stop threshold for the ambient conditions of the vehicle, use the instructions and the graph below:

1. Using the climate control sensor input display mode of the HDS, record the outside air temperature (SENSOR 3), the in-vehicle temperature (SENSOR 2), and the in-vehicle humidity (SENSOR A).
2. Draw a vertical line from the outside temperature value to the 80 percent relative humidity curve.
3. Draw a horizontal line from the 80 percent intersection to the right side of the graph.
4. Draw a vertical line from the in-vehicle temperature value to the top to the graph.
   • The auto idle stop humidity threshold is where the lines cross. Auto idle stop is disabled when the in-vehicle humidity is above this point, and it is enabled when the humidity is below this point.
   • In the example below, auto stop is disabled when the in-vehicle humidity exceeds about 30 percent. This is determined by an outside temperature of 45 °F (7 °C) and an in-vehicle temperature of 72 °F (22 °C).

The auto idle stop enable time depends on how close the in-vehicle humidity is to the calculated humidity threshold. The closer the in-vehicle value is to the threshold, the shorter the auto idle stop enable time will be. Auto idle stop may not occur if the values are too close.

Fig 1: In-Vehicle Humidity Auto Idle Stop Conditions Graph

Courtesy of AMERICAN HONDA MOTOR CO., INC.