What is the Ambient Temperature Sensor (Switch) all about?

Modern automotive HVAC systems have advanced by leaps and bounds over those used just a few years ago. Today, many high and even mid-range cars offer automatic climate control. This function basically allows you to “set it and forget it,” allowing the car’s computer to control the heating and cooling based on your preferred interior temperature. In order to do this, the computer needs information about not only the temperature inside the car, but also the ambient temperature outside the car.

The ambient temperature sensor (switch) is located either behind the front grille or in the front bumper. Its only job is to monitor air temperature (which it does through increasing/decreasing resistance in response to temperature fluctuations). This information is transmitted to the car’s computer, which then adjusts the climate control to meet your specifications.

If the ambient temperature sensor is damaged or fails, the car’s computer will not be able to automatically control the HVAC system, and the heater and air conditioner will only work in manual mode.

Keep in mind:

• Because of its location, the ambient temperature sensor can be easily damaged in even minor front-end collisions.
• Sensor failure is common even without an accident.

How it's done:

• The ambient temperature sensor switch is verified to see if it needs to be replaced
• The defective ambient temperature sensor switch is removed
• The new ambient temperature sensor switch is installed
• The ambient temperature sensor switch is tested for operation
• The vehicle is tested to ensure proper operation of the ambient temperature sensor switch

Our recommendation:

Without the information provided by the ambient temperature sensor, your car’s computer does not have sufficient data to control the interior temperature, and will revert to manual HVAC control. You’ll still be able to use your air conditioner and heater, but only in manual mode, not in auto. If you suspect a problem with the ambient temperature sensor, have it diagnosed by one of our expert mechanics and replaced if necessary.

What common symptoms indicate you may need to replace the Ambient Temperature Sensor (Switch)?

• HVAC auto mode will not work
• HVAC auto mode produces delivers inconsistent/incorrect operation
• HVAC will only work in manual mode
• Outside temperatures may display incorrectly

How important is this service?

Having automatic climate control is definitely a convenience, but not critical to the operation of your vehicle. The heater will still operate to clear the windows and provide heating and cooling on manual mode. If the ambient temperature sensor is faulty, have it replaced.