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I've been watching this for a month or so now and it's definitely odd. Basically, I think the sensor that reads the external temperature (as reported in the dash) is whacked. Anybody had experiences like this?

Data Point 1: At lunch today (11:30 in Boston) I headed out to run some errands and have lunch. The temperature gauge read 73 or so when I got in the car (it was probably actually a bit warmer than that). Roughly ninety minutes later when I pulled back into the office it read 96 or so. It probably did get a bit warmer during that hour and a half but no way it was that hot out.

Data Point 2: Driving home tonight I got in the car and it read 83. Thirty minutes later as I pulled into the driveway it read 103. No way it was much over 80, if it was over 80 at all. (It was a really nice day in Boston today, in fact - not an entirely common occurrence I must unfortunately report!).

Where is the sensor? Is the engine heat seeping to it? The temperature gauge in the dash never goes past straight vertical.

Clues? Thoughts? Anybody else have this oddity?

Can't say I noticed this behavior in, say, February, but maybe I just wasn't looking for it.

Shawn
 

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I have the exact same behaviour with my M5. I plan to address this at the next service in a couple of weeks, since it seems to be only a minor annoyance. basically, it reads around 90-100 after the cars been on for a while.

ME
 

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I asked one of the guys at the Spartanburg experience about this and he said they had to move the sensor for the M5 vs 540 or 528 and that they chose a "bad spot". No mention of any fix though.
It should be fixed because, currently mine is completely useless!
 

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The silver M5 that I drove at Spartanburg consistently thought it was 122 outside. It must be a common problem.
 

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Yeah, I see the same thing. The temp reading seems fairly accurate at lower temperatures and at night, but during a hot day it reads 10-25 degrees too warm.

Rick
 

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I brought my M5 in for a few problems, the outside temp being one of them. The tech told me that the temp probe is located under the front bumper, passenger side. The probe is picking up heat from the engine and it is a design flaw and they don't have a fix yet.
 

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The outside temperature probe is in a recess in one of the horizontal airflow panels between the bumper and the front wheelwell. It is behind the right fog light. It sticks downward at about a 45 degree angle.

In this location it will give fairly accurate readings when the car is in motion, particularly at interstate/freeway (autobahn) speeds. When you come to a stop (or at very low speeds) the heat from the engine, and to a lesser degree the brakes, isn't blown back under the car and it reaches the probe resulting in the incorrect (and always too high) readings.

For what its worth, my old E34 M5 had the same problem. The probe was located in a fake airbrake duct in the front airdam. I could control the temp readout by use of my brakes during city driving. The fix the factory guys suggested to me, which worked, was to relocate the probe to the air inlet for the alternator (which was fed from a duct in the other side of the airdam -- the E34 M5 didn't use ducts to cool the brakes, that was the function of the turbine vanes on the wheeels). This won't work on our cars -- the alternators are water cooled.

I don't think there is another place for the probe, except at the back of the car, that won't be affected by engine heat when the car is not moving. If I think of a fix I'll let you know. Till then I'll try to enjoy the comfortable 122 degree days my computer sometimes tells me we have.

Louis
 
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