What’s the Ambient Air Temperature Sensor? Symptoms and Replacement Cost

Modern vehicles are equipped with advanced climate control features, allowing drivers to control the exact temperature of certain parts of the cabin. One of the reasons the heating, ventilation, and air-conditioning (HVAC) system can do this effectively is because it has sensors that monitor the temperature of various parts of the vehicle. One of these sensors is the ambient temperature sensor, which is sometimes called the outside temperature sensor.

What Is the Ambient Air Temperature Sensor?

The ambient air temperature sensor is responsible for detecting the air temperature outside the vehicle’s cabin. It uses a negative temperature coefficient sensor, which is essentially a resistor whose resistance decreases when the temperature rises. The electronic temperature control system interprets the voltage received from the ambient air temperature sensor and compares it with the reading from the in-car temperature sensor. The temperature control system makes changes to variables like blower motor speed depending on the difference between these two readings.

The ambient temperature sensor input is available on the vehicle network and can be displayed on message center or heads up display.

The ambient air temperature sensor is usually attached to the inside of your vehicle’s bumper or grill. This location is important because the sensor is sensitive to temperature, and it needs to be shielded from sunlight and strong winds present during travel while still having access to the outside air. But the problem at idle is that sometimes radiator heat may skew the temperature reading unless the sensor is mounted by a panel to mitigate that issue. It varies from vehicle to vehicle.

The ambient air temperature sensor is usually attached to the inside of your vehicle’s bumper or grill. This location is important because the sensor is sensitive to temperature, and it needs to be shielded from sunlight and strong winds present during travel while still having access to the outside air.

Symptoms of a Bad Ambient Air Temperature Sensor

Vehicles in very hot or cold environments will require the HVAC system to work harder to achieve a comfortable cabin temperature. This small sensor is important because it dictates the performance of your HVAC system. Without it, the system won’t be aware of the temperature of the environment in which the car is operating. If you think your ambient air temperature sensor is broken, you should look out for these symptoms: Many climate control systems will flash an indicator or display a message if the ambient sensor goes offline for whatever reason.

 Many climate control systems will flash an indicator or display a message if the ambient sensor goes offline for whatever reason.

– Richard McCuistian, ASE Certified Master Automobile Technician

Compressor Clutch Won’t Engage

This doesn’t happen on every vehicle when the ambient sensor input is lost. It’s more likely to happen on vehicles with automatic climate control.

Since the compressor pulley is constantly rotated by an accessory belt, it has a clutch that connects the compressor to the pulley when the air-conditioning system (A/C) is turned on. Note however, that some newer A/C compressors don’t have a clutch. They just spin all the time, and a swash plate inside the compressor changes its angle to determine compressor operation. When the plate is vertical, the compressor isn’t pumping even though it’s spinning.

A faulty ambient air temperature sensor might prevent the A/C system from engaging the compressor. Without it, there won’t be any cold air flowing inside your cabin.

Incorrect Temperature Gauge Reading

An inaccurate reading on the vehicle’s message center is another indicator of a damaged or failed sensor. Most cars have a display on the dashboard that shows the outside temperature of the vehicle, which is usually detected by the ambient temperature sensor. If the gauge or indicator reading is off by more than a few degrees, then the sensor is likely faulty.

The HVAC System’s Automatic Mode Won’t Work

Modern vehicles have a button that sets the HVAC to auto mode, allowing the system to regulate its fan speed depending on the set temperature. The HVAC system will use the readings from the ambient and cabin temperature sensors and determine how to utilize the A/C system as necessary to keep the cabin cool. When the ambient temperature sensor fails, the system will lack a reference point and the setting might not work.

How Much Does an Ambient Air Temperature Sensor Cost?

Ambient air temperature sensors are around $10 to $100, depending on the part’s brand and the vehicle model it’s intended for.

Where to Get a New Ambient Air Temperature Sensor For Your Vehicle

A bad ambient temperature air sensor hampers your vehicle’s HVAC system. While it can’t stop you from going for a drive, it can make the trip less comfortable, especially when it’s freezing or scorching hot. Fortunately, CarParts.com won’t make you wait long for a replacement ambient temperature sensor.

Here at CarParts.com, we deliver the parts you need when you need them. Thanks to the strategic locations of our warehouses, you can get your order in as fast as two business days. We exclusively source our products from trusted manufacturers, ensuring you get your money’s worth. And if you have any questions about our products, you can contact our friendly and helpful customer service team for assistance.

Replace a bad ambient air temperature sensor before it leads to more severe problems. Check out our selection of reliable ambient temperature sensors at and shop now at CarParts.com.