Method for controlling an air conditioning (HVAC) system of a vehicle

Abstract

A method for controlling an air conditioning system (HVAC) (28) of a vehicle (20), comprising the following steps: repeatedly detecting an area size () of a window (26) of the vehicle (20) that is not covered with frost with a sensor (42) mounted adjacent to the window (26); Controlling the air conditioning system (28) with an air conditioning controller (46) such that it is operated in a defrost mode when the detected area size (48) that is not covered with frost is smaller than an area threshold; and Controlling the air conditioning system (28) with the air conditioning controller (46) to operate in an interior heating mode when the detected area size not covered with frost is equal to or greater than the area threshold; wherein the air conditioning controller (46) automatically switches the air conditioning system (28) from the defrost mode to the interior heating mode in response to the detected area size not covered with frost when it increases to a value equal to or greater than the area threshold; Detecting a temperature of an engine coolant with a coolant temperature sensor; Detecting an interior temperature within a passenger compartment (24) of the vehicle (20) with an air temperature sensor; Comparing the sensed interior temperature with a desired interior temperature to determine whether the sensed interior temperature is less than the desired interior temperature, or whether the sensed interior temperature is equal to or greater than the desired interior temperature; and Controlling the air conditioning system (28) to operate in both defrost mode and interior heating mode in response to the engine coolant temperature being equal to or greater than a threshold coolant temperature, and the sensed area size not covered with frost being equal to or greater than an intermediate area threshold and less than the area threshold, and the sensed interior temperature being less than the desired interior temperature.

Description

TECHNICAL FIELD

[0001] The disclosure relates to a method for controlling an air conditioning system of a vehicle.

[0002] Most vehicles have a heating, ventilation, and air conditioning (HVAC) system capable of operating in at least a defrost mode and / or an interior heating mode. When controlled to operate in defrost mode, the air conditioning system directs a flow of heated air directly onto an interior surface of the window to break up frost that has formed on an exterior surface of the window and / or to break up condensation that has formed on an interior surface of the window. When controlled to operate in interior heating mode, the air conditioning system directs a flow of heated air into a passenger compartment of the vehicle to warm the air within the passenger compartment to a desired interior temperature. The air conditioning system can also be controlled to operate in a split mode, in which both the defrost mode and the interior heating mode are applied simultaneously.Part of the warm air flow is directed onto the windows to demist / defrost them and another part of the warm air flow is directed into the interior to heat the interior air to the desired interior temperature.

[0003] DE 11 2013 003 527 T5 discloses a method for removing window fogging, in which fogging areas on the window pane are determined using temperature sensors. DE 11 2014 002 612 T5 discloses a vehicle air conditioning system that is particularly suitable for electric vehicles that are not powered by an internal combustion engine.

[0004] It is the object of the present invention to provide a method for controlling a vehicle air conditioning system with which the period for heating the interior air to the desired interior temperature can be efficiently shortened.

[0005] This problem is solved by the features of claim 1.

[0006] A (unclaimed) vehicle is also disclosed. The vehicle includes a body with a passenger compartment and includes a window. The vehicle further includes an air conditioning system operable in a defrost mode for defrosting the window or in an interior heating mode for heating the passenger compartment. An optical sensor is mounted adjacent to the window within the passenger compartment. The optical sensor is operable to detect light through the window. A light source is attached to the body outside the passenger compartment and mounted to emit light through the window. An air conditioning controller is mounted in communication with the optical sensor such that the optical sensor is operable to detect data regarding the light emitted by the light source and transmitted through the window and to transmit the detected data to the air conditioning controller.The air conditioning control includes tangible, non-volatile memory storing recorded computer-executable instructions, including an air conditioning control algorithm. The air conditioning control algorithm is operable on the processor to calculate a percentage of the window covered with frost based on the data detected by the optical sensor. The air conditioning control algorithm automatically controls the air conditioning system in defrost mode or interior heating mode based on the calculated percentage of the window covered with frost.

[0007] Accordingly, the air conditioning control receives data from the sensor next to the window and uses this data to calculate the percentage of the window covered with frost. The air conditioning control then automatically determines whether the air conditioning system should operate in defrost mode or interior heating mode based on the calculated percentage of the window not covered with frost. If the calculated percentage changes, i.e., increases to a percentage equal to or greater than the range threshold, the air conditioning control automatically switches the air conditioning system's operation from defrost mode to interior heating mode.By automatically switching the air conditioning system from defrost mode to interior heating mode once the window is sufficiently defrosted, rather than operating in defrost mode for a period of time after the window has been defrosted, thermal energy is transferred more quickly to heat the interior air, thereby reducing the time required to heat the interior air to the desired interior temperature.

[0008] The above features and advantages, as well as other features and advantages of the present teachings, can be readily derived from the following detailed description of the best modes for carrying out the teachings when considered in conjunction with the accompanying drawings. Fig. 1 is a schematic side view of a vehicle. Fig. 2 is a schematic plan view of a windshield of the vehicle, showing a portion of the windshield covered with frost and a portion of the windshield not covered with frost. Fig. 3 is a flowchart illustrating a method for controlling the vehicle's air conditioning system.

[0009] Those skilled in the art will recognize that terms such as "above," "below," "upward," "downward," "top," "bottom," etc., are used descriptively for the figures and do not represent limitations on the scope of the disclosure defined by the appended claims. Furthermore, the teachings herein may be described in terms of functional or logical block components or various processing steps, respectively. It should be noted that such block components may be constructed from any number of hardware, software, or firmware components configured to perform the specified functions.

[0010] In the figures, the corresponding numbers indicate the corresponding components in the different views, a vehicle is usually represented as 20 in Fig. 1. The vehicle 20 may include any type and / or configuration that includes a body 22 defining a passenger compartment 24. The body 22 includes a window 26. As in the embodiment in Fig. 1, the window 26 is a front window. However, it should be understood that the window 26 may include a side-facing window 26 or a rear-facing window 26.

[0011] The vehicle 20 further includes a heating, ventilation, and air conditioning (HVAC) system 28. The air conditioning system 28 includes, but is not limited to, a fan 29 for moving airflow through a system of ducts 30, a heater core 32 for exchanging heat from an engine coolant to an airflow, and an evaporator (not shown) for removing heat from the airflow. The system of ducts 30 includes one or more valves, dampers, or similar control devices to control airflow between the various outlets. For example, the system of ducts 30 includes at least one defroster outlet 34 mounted adjacent the window 26 for directing airflow directly onto the window 26. The system of ducts 30 also includes at least one interior outlet 36 mounted to direct air flow into the passenger compartment 24 for heating and / or cooling the air within the passenger compartment 24.

[0012] The air conditioning system 28 is operable in at least one defrost mode and one interior heating mode. It should be noted that the air conditioning system 28 is operable in other operating modes not described herein. When the air conditioning system 28 is controlled to operate in the defrost mode, the system of ducts 30 directs the airflow through the heater core 32 to remove heat from an engine coolant and then directs the warm airflow toward the window 26, generally indicated by arrow 38, to either defrost an exterior surface of the window 26 and / or defog an interior surface of the window 26.When the air conditioning system 28 is controlled to operate in the cabin heating mode, the system of ducts 30 directs airflow through the heater core 32 to remove heat from the engine coolant and then directs the heated airflow into the passenger compartment 24, generally indicated by arrow 40, to heat the passenger compartment 24 to a desired interior temperature. The cabin heating mode may include any HVAC operating mode that does not directly direct airflow onto the window 26 to defrost the window 26. For example, the cabin heating mode may direct the heated airflow toward an occupant footwell via a lower outlet or toward an occupant torso area via an outlet mounted on the interior trim or instrument panel. It should be noted that the cabin heating mode may include other heating mode options not specifically mentioned or described herein.The air conditioning system 28 can be operated in a split mode in which a portion of the warm air flow is directed to the window 26, i.e., the defrost mode, and another portion of the warm air flow is simultaneously directed into the passenger compartment 24, i.e., the interior heating mode.

[0013] The vehicle 20 further includes a sensor 42. The sensor 42 is mounted adjacent the window 26 within the passenger compartment 24. In one embodiment, the sensor 42 is operable to detect light and / or objects through the window 26. In the embodiment in Fig. 1, the sensor 42 is mounted as a forward-facing sensor 42 for detecting objects and / or light through the windshield of the vehicle 20. The sensor 42 may include, but is not limited to, an optical sensor 42, such as a camera or a light sensor 42. For example, in one embodiment, the sensor 42 may include a forward-facing camera that detects objects in front of the vehicle 20 and / or lane lines. It should be noted that, in addition to the method described below, the sensor 42 may be used to perform some other functions related to controlling the vehicle 20, such as object avoidance or lane correction. Furthermore, it should be noted that the sensor 42 may include other types of sensors, such as a capacitance sensor on the window 26. Thus, the sensor 42 should not be limited to the optical sensor embodiments (e.g.,a camera or a light sensor) or the capacitance sensor described herein. Rather, the term "sensor" should be interpreted more broadly to include any type of sensor capable of collecting data that the climate control system 46 can use to calculate the percentage of frost on the window 26.

[0014] If the sensor 42 is a light sensor 42, it may be necessary to equip the vehicle 20 with a light source 44 mounted on the body 22 outside the passenger compartment 24 and positioned to emit light through the window 26 into the interior of the passenger compartment 24 and onto the sensor 42 so that the sensor 42 can detect the light shining through the window 26. For example, if the sensor 42 is an infrared light sensor 42, an infrared light source may be mounted outside the passenger compartment 24 to shine through the window 26. Such an optical sensor 42 would be operable to detect the data associated with the light from the light source 44 and transmit it through the window 26.

[0015] The vehicle 20 further includes an air conditioning controller 46. The air conditioning controller 46 is mounted in communication with the sensor 42, and the sensor 42 transmits the sensed data to the air conditioning controller 46. The air conditioning controller 46 is operable to control an air conditioning system 28 based at least in part on the data sensed by the sensor 42. The air conditioning controller 46 may include a computer and / or processor and may have all software, hardware, memory, algorithms, connections, sensors, etc., necessary to manage and operate the air conditioning controller 46. As such, a method described below and generally in Fig. 3, may be executed as a program or algorithm operable on the air conditioning controller 46. It should be noted that the air conditioning controller 46 may include any device capable of analyzing data from various sensors or other devices, comparing data, making the necessary decisions required to control the air conditioning system 28, and performing the necessary operational steps to control the operation of the air conditioning system 28.

[0016] The air conditioning controller 46 includes tangible, non-volatile memory storing computer-executable instructions, including an air conditioning control algorithm. The controller further includes a processor operable to execute the air conditioning control algorithm to control the air conditioning system 28 between the defrost mode, the interior heating mode, and / or the split mode. The air conditioning control algorithm uses the data from the vehicle sensor(s) 42 to determine the percentage of the window 26 covered with frost and to control the air conditioning system 28 between the defrost mode and the interior heating mode based on the percentage of the window 26 covered with frost.

[0017] The air conditioning controller 46 may be embodied as one or more digital computers or host computers, each having one or more processors, read-only memory (ROM), random access memory (RAM), electrically programmable read-only memory (EPROM), optical drives, magnetic drives, etc., a high-speed clock, analog / digital (A / D) circuits, digital / analog (D / A) circuits, and all necessary input / output (I / O) circuits, input / output devices and communication interfaces, as well as signal conditioning and buffer circuits.

[0018] Computer-readable storage may include any volatile / non-volatile medium that participates in the provision of data or computer-readable instructions. The storage may be non-volatile or volatile. Non-volatile media may include, for example, optical or magnetic floppy disks and other persistent storage. Volatile media may include, for example, dynamic random access memory (DRAM) that forms main memory. Other examples of storage embodiments include a floppy disk, a flexible disk or hard disk, magnetic tape or other magnetic media, a CD-ROM, DVD, or other optical media, as well as other possible storage elements such as flash memory.

[0019] The air conditioning controller 46 includes tangible, non-volatile memory on which recorded computer-executable instructions are stored, including the air conditioning control algorithm. The air conditioning control algorithm implements the method for controlling the air conditioning system 28 described below. Referring to Fig. 3, the method includes continuously and repeatedly detecting an area of ​​a window 26 of the vehicle 20 that is not covered with frost with a sensor 42 mounted adjacent the window 26. The detection of the area of ​​the window 26 that is not covered with frost is generally indicated by field 100 in Fig. 3. With reference to Fig. 2, the area of ​​window 26 not covered with frost is generally depicted as the clear portion 48 of window 26, and the area of ​​window 26 covered with frost is generally depicted as the shaded portion 50 of window 26. Sensor 42 may appropriately collect data relating to the area of ​​window 26 not covered with frost. Because the frost blocks, at least to some extent, the portions of window 26 covered with frost and the portions of window 26 not covered with frost transmit different intensities of light through window 26.Accordingly, the sensor 42 can be programmed to detect portions of the window 26 that transmit a high amount of light where no frost is present in portion 48, and other portions of the window 26 that transmit less light where frost is present in portion 50. This data can be transmitted to the air conditioning control 46 so that the air conditioning control 46 can determine a size of the area of ​​the surface that is or is not covered with frost.

[0020] In another example, the sensor 42 may be configured or programmed to collect data regarding a boundary line 52 at the edge of the intersection between portions of the window 26 covered with frost and portions not covered with frost. The climate control system 46 may then use the data regarding the collected boundary line 52 to determine a size of the area of ​​the window 26 that is or is not covered with frost. In a further alternative embodiment, the sensor 42 may be configured to detect or sense objects, such as a hood or body wiring of the body 22.The climate control 46 may then be able to determine the size of the area of ​​the window 26 covered with frost based on the amount of the hood / vehicle 20 and body 22 visible through the window 26 to the sensor 42 through the unfrosted areas of the window 26. It should be noted that the data collected by the sensor 42 and the manner in which the sensor 42 and / or the climate control 46 determines the area of ​​the window 26 covered and uncovered with frost may vary from the embodiments described herein.

[0021] Once the sensor 42 has detected the area of ​​the window 26 that is covered and uncovered with frost, the air conditioning control 46 can calculate a percentage of the window 26 that is not covered with frost based on the data detected by the sensor 42 regarding the area of ​​the window 26 that is not covered with frost. The calculation of the percentage of the window 26 that is not covered with frost is generally indicated by field 102 in Fig. 3. The air conditioning control 46 may be preprogrammed with a total area of ​​the window 26 such that once an area of ​​the window 26 that is not covered with frost can be detected or determined by the sensor 42 and / or the air conditioning control 46, the air conditioning control 46 may use simple mathematical calculations to calculate the percentage of the window 26 that is not covered with frost. The process of detecting the area of ​​the window 26 that is not covered with frost and calculating the percentage of the window 26 that is not covered with frost is performed continuously or repeatedly such that the air conditioning control 46 knows the current state of the window 26.

[0022] The temperature of the engine coolant is also continuously or repeatedly sensed by a coolant temperature sensor of the vehicle 20. The sensing of the engine coolant temperature is generally indicated by field 104 in Fig. 3. The engine coolant temperature sensor detects the temperature of the coolant circulating through an engine of the vehicle 20 and transmits the detected temperature to the air conditioning controller 46. The engine coolant temperature sensor and its operation are well known to those skilled in the art and therefore will not be described in detail herein. The detected engine coolant temperature is used for several different algorithms of the vehicle 20 and is typically available via a vehicle data line.

[0023] The air conditioning controller 46 compares the sensed engine coolant temperature to a threshold coolant temperature to determine whether the engine coolant temperature is less than the threshold coolant temperature, or whether the engine coolant temperature is equal to or greater than the threshold coolant temperature. The threshold coolant temperature is a predetermined temperature that the engine coolant should reach before being used to heat the airflow through the air conditioning system 28. Before the engine coolant reaches the threshold coolant temperature, all heat within the engine coolant should be directed toward heating the engine and not used to heat the airflow through the air conditioning system 28. The threshold coolant temperature may, for example, be defined equal to a temperature of approximately 20°C.

[0024] An interior temperature within the passenger compartment 24 of the vehicle 20 is also continuously and / or repeatedly sensed with an air temperature sensor. The sensing of the interior temperature is generally indicated by field 106 in Fig. 3. The air temperature sensor may be part of the air conditioning system 28 and senses the air temperature within the passenger compartment 24. The air temperature is transmitted to the air conditioning control 46, so that the air conditioning control 46 compares the sensed interior temperature to a desired interior temperature to determine whether the sensed interior temperature is less than the desired interior temperature, or whether the sensed interior temperature is equal to or greater than the desired interior temperature. The desired interior temperature is the air temperature within the passenger compartment 24 that the air conditioning system 28 is attempting to achieve. The desired interior temperature is preferably a user-defined value and can be entered into the air conditioning control 46 by a user setting a desired temperature.

[0025] The air conditioning control 46 compares the percentage of the window 26 that is not covered with frost to an area threshold to determine whether the percentage of the window 26 that is not covered with frost is less than or equal to the area threshold, or whether the percentage of the window 26 that is covered with frost is greater than the area threshold. The area threshold is a minimum area of ​​the window 26 that must be cleared of frost or mist before the HVAC fully switches to the interior heating mode. For example, the area threshold may be defined as equal to between 50% and 100% of the total area of ​​the window 26. The area threshold may be a user-defined value entered into the air conditioning control 46 or a predefined value entered into the air conditioning control 46.

[0026] As generally stated in field 108 in Fig. 3, the air conditioning control 46 compares the percentage of the window 26 that is not covered with frost to the area threshold, the sensed engine coolant temperature to the coolant threshold temperature, and the sensed interior temperature to the desired interior temperature. If the air conditioning control 46 determines that the sensed interior temperature is less than the desired interior temperature, the percentage of the window 26 that is not covered with frost is less than the area threshold, and the sensed engine coolant temperature is less than the coolant threshold temperature, generally indicated by field 110, then the air conditioning control 46 controls the air conditioning system 28 to operate in the defrost mode. Referring to Fig. 3, if the air conditioning control 46 determines that the interior temperature is less than the desired interior temperature, the detected area not covered with frost is less than the area threshold and the temperature of the engine coolant is less than the threshold temperature of the coolant, generally indicated by field 110, then the air conditioning control 46 controls the fan 29 at a first speed, generally indicated by field 111 in Fig. 3. The first speed may be defined as a 0% duty cycle of the fan 29, meaning that the fan 29 is not running or is defined to be equal to a duty cycle greater than 0% but less than 100%. For example, the first speed may be defined as a 30% duty cycle of the fan 29. The air conditioning system 28 may operate the fan 29 at the first speed when the engine coolant temperature is less than the threshold coolant temperature, so that the air conditioning system 28 does not draw too much heat from the engine coolant and the engine can warm up quickly.

[0027] If the air conditioning controller 46 determines that the sensed interior temperature is not less than the desired interior temperature, the percentage of the window not covered with frost is not less than the range threshold, and / or the sensed engine coolant temperature is not less than the threshold coolant temperature, generally indicated by box 112, then the air conditioning controller 46 determines whether the sensed interior temperature is less than the desired interior temperature, the percentage of the window not covered with frost is less than the range threshold, and the sensed engine coolant temperature is equal to or greater than the threshold coolant temperature, generally indicated by box 114 in Fig.3. If the air conditioning control determines that the sensed interior temperature is less than the desired interior temperature, the percentage of the window not covered with frost is less than the range threshold, and the sensed engine coolant temperature is equal to or greater than the threshold coolant temperature, generally indicated by field 116, then the air conditioning control controls the fan 29 to operate at a second speed, generally indicated by field 118. The second speed is different from the first speed. The second speed may be defined, for example, as a 100% duty cycle of the fan 29, i.e., the fan 29 operates at full speed.

[0028] As long as the percentage of window 26 not covered with frost is less than the area threshold, climate control 46 controls air conditioning system 28 to operate in defrost mode. However, if climate control 46 determines that the sensed interior temperature is not less than the desired interior temperature, the percentage of window not covered with frost is not less than the area threshold, and / or the sensed engine coolant temperature is not equal to or greater than the coolant threshold temperature, generally indicated by field 120, then the climate control compares the sensed area not covered with frost to an intermediate area threshold, generally indicated by field 122. The intermediate area threshold may be defined equal to a value between 10% and 90% of the total area of ​​window 26.If the air conditioning control 46 determines that the sensed area not covered with frost is equal to or greater than the intermediate area threshold but less than the area threshold, the engine coolant temperature is equal to or greater than the threshold coolant temperature, and the sensed interior temperature is less than the desired interior temperature, generally indicated by box 124, then the air conditioning control 46 may control the air conditioning system 28 to operate in split mode, that is, to operate in both the defrost mode and the interior heating mode simultaneously, generally indicated by box 126. In doing so, once the window 26 begins to defrost and is partially defrosted, a portion of the heated airflow is directed to warm the passenger compartment 24.

[0029] If the detected area not covered with frost is equal to or greater than the area threshold and the air temperature within the passenger compartment 24 is less than the desired interior temperature, the HVAC controller 46 controls the HVAC system 28 in the interior heating mode to operate the fan 29 at a 100% duty cycle to heat the air within the interior, generally indicated by box 128. The HVAC operates the HVAC system 28 in the interior heating mode until the air temperature within the passenger compartment 24 reaches the desired interior temperature, at which time the HVAC controller 46 controls the fan 29 at a lower duty cycle, such as a 25% duty cycle, generally indicated by box 130, until the user inputs a command to the HVAC control 46 to change the control schedule.

[0030] The air conditioning controller 46 automatically switches the air conditioning system 28 from defrost mode to interior heating mode when the detected area not covered with frost increases to a value equal to or greater than the area threshold. Accordingly, the switch from defrost mode to interior heating mode is not based on a preset time at which the window 26 may or may not be defrosted. Rather, the decision to switch from defrost mode to interior heating mode is based on the current, actual conditions of the window 26. As a result, the air conditioning system 28 operates in defrost mode only until the window 26 is defrosted and does not spend additional time directing the heated air to the window 26 after the window 26 is defrosted.By automatically switching from defrost mode to interior heating mode when the detected area not covered with frost is a value equal to or greater than the area threshold, heat can be conducted more quickly to warm the air in the passenger compartment 24.

[0031] The method described above is particularly applicable to vehicles 20 with remote start capabilities, in which the vehicle 20 can be remotely started via a portable handheld device, such as a key fob, a mobile phone, a tablet, or other mobile device. The climate control 46 can be connected and communicated with the portable handheld device such that the vehicle 20 can be remotely started and a desired interior temperature can be input to the climate control 46 via the portable handheld device. In doing so, a user can define the desired temperature for the passenger compartment 24.The air conditioning control 46 will, as described above, first control the air conditioning system 28 to defrost the window 26, for example, the windshield, and then automatically switch to the interior heating mode of the passenger compartment 24 to the desired interior temperature when the window 26 is defrosted. The method described above minimizes the amount of time required to defrost the window 26 and heat the passenger compartment 24 to the desired interior temperature.

Claims

[1] A method for controlling an air conditioning system (HVAC) (28) of a vehicle (20), comprising the following steps: repeatedly detecting an area size () of a window (26) of the vehicle (20) that is not covered with frost with a sensor (42) mounted adjacent to the window (26); Controlling the air conditioning system (28) with an air conditioning controller (46) such that it is operated in a defrost mode when the detected area size (48) that is not covered with frost is smaller than an area threshold; and Controlling the air conditioning system (28) with the air conditioning controller (46) to operate in an interior heating mode when the detected area size not covered with frost is equal to or greater than the area threshold; wherein the air conditioning controller (46) automatically switches the air conditioning system (28) from the defrost mode to the interior heating mode in response to the detected area size not covered with frost when it increases to a value equal to or greater than the area threshold; Detecting a temperature of an engine coolant with a coolant temperature sensor; Detecting an interior temperature within a passenger compartment (24) of the vehicle (20) with an air temperature sensor; Comparing the sensed interior temperature with a desired interior temperature to determine whether the sensed interior temperature is less than the desired interior temperature, or whether the sensed interior temperature is equal to or greater than the desired interior temperature; and Controlling the air conditioning system (28) to operate in both defrost mode and interior heating mode in response to the engine coolant temperature being equal to or greater than a threshold coolant temperature, and the sensed area size not covered with frost being equal to or greater than an intermediate area threshold and less than the area threshold, and the sensed interior temperature being less than the desired interior temperature. [2] The method of claim 1, further comprising comparing the temperature of the engine coolant to the threshold temperature of the coolant to determine whether the temperature of the engine coolant is less than the threshold temperature of the coolant, or whether the temperature of the engine coolant is equal to or greater than the threshold temperature of the coolant. [3] The method of claim 2, wherein controlling the air conditioning system (28) to operate in the defrost mode comprises controlling a fan (29) to operate at a first speed in response to the engine coolant temperature being less than the threshold coolant temperature. [4] The method of claim 3, wherein controlling the air conditioning system (28) to operate in the defrost mode comprises controlling a fan (29) to operate at a second speed, different from the first speed, in response to the engine coolant temperature being equal to or greater than the threshold coolant temperature. [5] The method of claim 1, wherein the sensor (42) comprises an optical sensor within the passenger compartment (24) for detecting objects through the window (26). [6] The method of claim 1, wherein the vehicle (20) includes a light source (44) mounted outside the passenger compartment (24) and operable to emit light through the window (26) and into the passenger compartment (24), and wherein the sensor (42) is mounted inside the passenger compartment (24) to detect the light from the light source (44).

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