Method and apparatus for detecting the operation of an engine-independent auxiliary heater and for diagnosing a coolant temperature of a motor vehicle
A method and apparatus for detecting the operation of an engine-independent auxiliary heater in a cooling system with multiple coolant circuits in a vehicle system with an auxiliary heater. On or after activating the vehicle system for a cold start, a shut-off valve is opened between a first coolant circuit with the auxiliary heater and a second coolant circuit with the coolant temperature sensor. A coolant pump is activated so that coolant from the first coolant circuit flushes around the coolant temperature sensor. A time course of a temperature reading from the coolant temperature sensor is performed for a predetermined period of time from the time the vehicle system is activated. A gradient of the temperature reading curve is determined. The gradient of the temperature reading curve is evaluated using a threshold value comparison to determine whether the auxiliary heater was activated before the cold start.
1 . A method to detect an operation of an engine-independent auxiliary heater in a cooling system with multiple coolant circuits in a vehicle system with an auxiliary heater, the method comprising:
opening, on or after activating the vehicle system for a cold start, a shut-off valve between a first coolant circuit with the auxiliary heater and a second coolant circuit with a coolant temperature sensor and activating a coolant pump so that coolant from the first coolant circuit flows about the coolant temperature sensor;
recording a time course of a temperature reading from the coolant temperature sensor for a predetermined period of time from the time the vehicle system is activated;
determining a course of the gradient of the temperature reading; and
evaluating the course of the gradient of the temperature reading curve using a threshold value comparison to determine whether the auxiliary heater was activated before the cold start.
2 . The method according to claim 1 , wherein the threshold value comparison is carried out depending on an integration value of the gradient of the course of the temperature reading.
3 . The method according to claim 2 , wherein it is determined that the auxiliary heater was activated prior to the cold start when the integration value exceeds a predetermined threshold value.
4 . The method according to claim 3 , wherein the threshold value is fixed or is determined depending on an ambient temperature.
5 . The method according to claim 1 , wherein the threshold value comparison is carried out depending on an integration value of an amount of the gradient of the course of the temperature reading.
6 . The method according to claim 1 , wherein a diagnosis of the coolant temperature sensor is performed or released only if it is found that the auxiliary heater was not activated prior to the cold start.
7 . A vehicle system of a vehicle, the system comprising:
a first coolant circuit of a cooling system with an auxiliary heater;
a second coolant circuit of the cooling system with a coolant temperature sensor;
a shut-off valve between the first coolant circuit and the second coolant circuit;
a coolant pump; and
a control unit configured to perform the method according to claim 1 .