‘It’s never going to be exactly accurate:’ The thermometer in your vehicle isn’t really reliable

KANSAS CITY, Mo. – You shouldn't trust the thermometer in your vehicles to accurately tell the temperature outside, but they do serve a purpose, according to mechanics.

Jeff Baker, a mechanic for 17 years, said the temperature reading you see on your dashboard isn’t necessarily a thermometer.

“There’s a sensor outside called the ambient air temp sensor that reads the outside air,” Baker said. “It tells your computer whether the temperature outside is OK for your air conditioning to operate.”

Baker said ambient air temperature sensors send messages to your air conditioner. If it’s too hot outside, the air conditioner knows to work harder.

“If that sensor starts to fail, you can get incorrect readings inside,” he said. “Once that starts happening, you get lower efficiency cooling, and it might not work at all.”

The sensors are usually located in front of the grill of your vehicle or on the either side of the bumper.

"All those parts and stuff that are around it, it’s all hot, too,” he said. “And if you’re talking about a bunch of black components, black components absorb all that heat.”

FOX4 wanted to see just how inaccurate the readings can be when it’s extremely hot outside.

Baker’s car had been sitting in direct sunlight for hours when he to start it. The sensor showed it was 109 degrees outside.

“If you trust that, you’re just going to think everything else is wrong,” Baker said.

The official temperature at the downtown airport at the time of the test was 97 degrees. That's a 12-degree difference.

FOX4 meteorologist Joe Lauria wasn’t surprised by the difference in temperature.

“It’s getting the heat from the sun,” Lauria said. “It’s also getting the heat bouncing up from the pavement, which is usually hotter than the air temperature.”

The FOX4 weather team uses sensors that are in weather instrument shelters.

“These are typically about 6 feet off the ground. They’re painted in white,” Lauria explained. “They have ventilation to allow air to circulate, but they’re always taken in the shade."

Baker said while the temperature reading in your vehicle might skyrocket when you first start it, it should drop once you start driving.

“It just takes a minute because that heat just builds, and it holds it until you get a bit of air flow to it and it’s gone,” Baker said. “It’s never going to be exactly accurate and never works 100% of the time.”

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