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Outside ambient air temp reading high. 135f and around 115 when moving even in 95-100 Phoenix temperature. Ordered and replaced sensor with oem part. Correctly mounted and splash shields all back in place.
thoughts on next steps since sensor already replaced and mounting verified?
Outside ambient air temp reading high. 135f and around 115 when moving even in 95-100 Phoenix temperature. Ordered and replaced sensor with oem part. Correctly mounted and splash shields all back in place.
thoughts on next steps since sensor already replaced and mounting verified?
I always expect the sensor to read higher than true ambient, due to its location just inches above the pavement, especially during this heat wave. It's like watching an F1 race where they give the air temp, followed by the track temp, which is always much higher, as the sun's heat is absorbed by the black pavement. In Summer heat, the pavement seldom gets a chance to cool overnight by much. And sitting in front of a hot radiator probably doesn't help.
The discrepancy is much less during the Winter, when the pavement temp is closer to the ambient air temp. Seldom more than a degree difference when the ground is frozen.
Because of this, I wouldn't bother replacing this sensor at all. Money wasted, IMO.
But I do question why MB locates it where it does (same general area on every MB I've seen}. A more practical location would be high in the upper grille, or in the engine intake tube. But no one asks me...
I recall that main purpose of the sensor is to warn the driver about potential road freeze, what would explain low position.
The sensor will always be affected when car is park, by engine temperature and/or sun exposure, but I found it pretty accurate when rolling.
AC is set by this sensor as well, so don't ignore bad readings.
On my E400, it is located on LEFT bumper fake air grille
I tried insulating it so that it won't go too hot too fast at traffic jam or a stand still, because the cooling air turbulence does reach its rear side of the sensor body and transfer heat to the sensor element https://www.ebay.co.uk/itm/223479398539
Does the insulation work ? Well, not as good as I expected. The key is car must be moving at some decent speed.
This is fun at the track, no fast driving on the straight, just eating up the corners only.
See how the AAT sensor behaves vs wind speed. Zone 1A and 1B is driver change at the pit, between me and my cousin. Zone 2 and 3 is waiting at the car park outside the pit/track before and after the run.
Leaving zone 2
Into zone 1B and leaving zone 1B , this is like 1 celcius increase per 2 seconds when car stop , zero speed.
W212 M276 DELA 30 ; W211 OM642 ; R107 M117, Sierra 1500 LZ0
Mine has an odd behavior, especially if the car has just been soaked (rain or wet). It will get "stuck" at the same temperature for 15+ minutes and then adjust itself to the real temperature eventually. None of my other mercedes have that problem. It's always interesting when it's been sitting in the sun and displays 115 and then after a few minutes of being cooled by virtue of moving it drops down to 93.
07-24-2022, 04:34 PM
OCD + Data Junkie I am, Certified.
Certified... LOL 
