External temperature sensor

alex

Member
Hello everyone, first post on here so treat me gently! It's actually not my car but my wife Rebecca's (who is on here as... err .... Rebecca :D ).

We've noticed that the external temperature is overreading - it's consistently about 3 degrees over what the temperature actually is. It's been in to a dealer, and strangely they couldn't find anything wrong... Today is the first day I've driven the car since, and low and behold the car was saying it was 14C when it was actually about 11.5C (as verified by my own car, and a temperature readout on a building).

So, seeing as Audi can't find the problem, I was thinking of just changing the temp sensor myself but I don't know where it is located. On my MK4 Golf it's down behind the front bumper on the passenger side, but rather than take everything apart and find it not there I thought I would register and check.

Is changing the sensor relatively easy?

Cheers

Alex.
 
it's in the middle of the front grille, the one below the numberplate.
So take out the foglight grilles and then remove the middle one (yes, you must do it this way round) and then you should be able to access the sensor.

I've never heard of anyone actually having to change it, though. Ever. Strange. Maybe there's calibration for it in VCDS / VAG-COM?

Bret
 
Thanks for replying, Brett - appreciate your thoughts!

I've had a look around online, and there doesn't appear to be any calibration potential inside VAG-COM/VCDS (and there appear to be a lot of people with VAG cars who have temperature sensors that are over-reading by between 2 and 5C).

Should I try changing the sensor, or not worry? The thing I'm concerned about is that if it's misreading the temperature, won't that affect fuelling and the Climate Control functions if the car thinks it's warmer than it is?
 
Mine said it was 14.C yesterday and it definitely was not. i don't think it is very accurate

Chris
 
mine is tendentially extremely accurate until I put in the winter blocked-off-grill. Then it's wrong.

The algorithm is pretty complex and includes taking speed into account to give accurate readings. If we're talking 2-3C out, I don't really see an issue. It's annoying if it's misreading around freezing, but then even below 3-4C life gets interesting fast, so I'd not worry too much.

Bret
 
Both of our A2's are also optimistic by 2-3C. I do wonder if there's a coating that wears with age on the thermistor that causes the inaccuracy. I think there is a good chance that a new sensor would cure the problem. It's a shame there is no calibration available in VCDS to counter act this wear.

Regards Rob.
 
My A2 1.4 SE has outside air temp reading 4 to 5 degrees above the actual temperature. The Audi main dealer changed the sensor but the fault still remained. They wanted the car another hour or so to investigate but I decided it was not worth the main dealer expense. Surely there must be a common cause if so many VAG cars have the problem.
 
My A2 1.4 SE has outside air temp reading 4 to 5 degrees above the actual temperature. The Audi main dealer changed the sensor but the fault still remained. They wanted the car another hour or so to investigate but I decided it was not worth the main dealer expense. Surely there must be a common cause if so many VAG cars have the problem.

There are many factors which could affect the temperature behind the bumper so a good starting point would be to measure the actual temp close to the sensor using a mercury thermometer. I'd guess a reasonable tolerance for the sensor would be + or - 2degC. If the difference is greater then check / clean the wiring connections to reduce the effect of increased resistance due to oxidation.

Cheers Spike
 
At the end of the day, we're talking about a temperature sensor which is quite close to the engine itself. It's never going to read the same figure as a thermometer which is well away from the engine.
 
Hi all, bit of an update for you - we've had the temperature sensor changed under warranty this week, and with it being sat cold on the drive it is reading 8C when the outside temperature is actually 3.6C. This is on a new sensor, with no residual heat from the engine.

Clearly then, it's not the sensor. Where next to check?
 
I read online that you can get diagnostic information out of the climate unit, so I spent *forever* this afternoon trying to make this work only to read a little later that this function isn't available on the A2 :confused:

Instead, I dug out my old VAG-COM cable and VCDS-Lite, and attempted to have a fiddle with that to attempt to see what info the sensor was actually sending.

After much faffing around, I finally managed to get VCDS-Lite to communicate with the Auto-HVAC module, but I don't have a label file so I don't know what measuring block I should be looking at to query the sensors. Can anybody help at all?
 
Back
Top