audi49t

My B7 S4 ambient temperature consistently reads high at higher outside temperatures. It's accurate around freezing, but about 8 degrees high at 90F. Any way to change scaling or add an offset using vag-com?
Thanks

Uwe@Ross-Tech.com

I don't think there is. However, the behavior you're seeing is fairly typical -- high ambient temperatures tend cause even higher temperatures at the sensor due to factors like heat radiating from paved surfaces and heat from the engine getting to the sensor. The temperature reported by the weather guy isn't measured in close proximity to a paved surface and a hot engine.

-Uwe-

mdernst

Exactly. And while the display of ambient temperature in all weather types is convenient and accurate for the location of the sensor, I believe its primary purpose is to warn the driver when temperatures close to the road surface are cold enough for ice to form on the road. That is why the sensors are generally located close to the bottom of the car near the road and why they pick up a lot of radiated heat in the summer from the black top/concrete.

If you were to change it then you might screw up an accurate winter time reading.

Mike

audi49t

Thanks for the replies, guys... I appreciate it. I've heard similar answers before, but am skeptical that those are the reasons. In my old B5 A4, the ambient temperature is measured basically in a similar location and it read spot on at all times. I know that the V8 generates a lot more heat, so it makes sense that we'd think that is a factor. However, it's generating the same amount of heat at freezing as it is at 90F (I think)... the coolant temperature is the same for both ambients. And if i'm going 60mph, most of the air hitting the temperature sensor is frome the front (convected to the sensor)... i would think that ambient (and not radiation from elsewhere) would dominate. I know this is common on the S4, but still it's frustrating that it's so far off. Thanks.