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Where is the thermometer on a car located?
August 24, 2006 11:16 PM   Subscribe

Where is the thermometer on a car typically located? Dashboard temp read-outs always seem absurd.

Everytime I notice a temperature read-out on a car dashboard, it's always seemed ludicrous to me. Today, the temperature was about 92 in Sacramento, but the digital readout in my parents' Volvo made the bold claim that SOMEthing was 115 degrees F.

What is the typical location for this thermometer in a car?

What environment is this read-out supposed to be telling you about? Outside the car? The car's interior?

Where on a car could you put a thermometer, such that you would minimize the chance of a biased result?
posted by k7lim to Technology (9 answers total)
 
the temp published by the weather guys is defined as being in a shaded, ventilated area with no solar radiation on it. That means it doesn't matter what colour the thermometer is made of nor what it is mounted to - radiation absorption plays no part in the reading, just conduction from the air.

You put the car out in the sun, it gets a hell of a lot hotter. How much hotter depends on the car and where in the car the thermometer goes, which makes that a bad way of publishing temperatures because every car is different.

Where it is in your car, I have no idea.
posted by polyglot at 11:59 PM on August 24, 2006


Also it's worth pointing out that the air over black roads will probably be hotter than the air over respiring plants.
posted by aubilenon at 12:08 AM on August 25, 2006


It depends on the car, of course.
Two popular places are the side mirrors and the underside of the front bumper.

Late 90's Volvo outside temp sensors are located under the front bumper. They can misbehave if they have come loose or if they've got a short.
Is the temp believable when the car is parked overnight? If it is, then the sensor is probably just loose or sticking into a hot air source. If it's wildly off after sitting overnight, it may be a bad sensor.

As for what it tells you, depends on the display. Usually the display on the instrument cluster is the outside temp, with the inside temp displayed somewhere near the heater controls.
posted by madajb at 12:22 AM on August 25, 2006


Also, they are usually fairly accurate.
But they take a while to adjust if the car has been sitting hot for a while or if you are in bumper to bumper traffic.
posted by madajb at 12:24 AM on August 25, 2006


I have a Durango and mine is under the hood. I think it's reading the air temp of the air coming into the engine.

It reads 5-10 hot in the summer, and seems to be pretty close in cooler weather.
posted by COD at 4:39 AM on August 25, 2006


Polyglot and COD both have it.

The display is showing the temperature measured at the engine's intake manifold ... but more importantly, the temperature where you are (usually a paved road) will often be higher than the official temperature at the airport that was measured in the shade.

When I first got my car with a temp display, I thought it must be inaccurate, but I've come to accept that it's accurate ... it's just that temperatures can vary considerably. Especially while on a freeway on a sunny day.
posted by pmurray63 at 6:53 AM on August 25, 2006


On my Audi the sensor is located a few inches in front of the radiator and A/C condensor, but behind the bumper. If it has been sitting for a while, the sensor gets heat soaked and reads a bit higher, but once I'm moving comes down to an accurate level.
posted by kableh at 7:09 AM on August 25, 2006


Usually somewhere around the front bumper. As others have said, it can take a few minutes of driving at speed to allow it to reach ambient temperature after sitting in the sun, leaving a warm garage, etc.
posted by caddis at 8:29 AM on August 25, 2006


The owner's manual for my late-model Volvo says the temperature on the dashboard displays the temperature of the road - not the air. Yours may be the same - 115 degrees does not sound outrageous for asphalt.
posted by peppermint22 at 2:22 PM on August 25, 2006


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