Temperature sensor

[jimbob35]

Hi all,

Are these external sensors generally accurate? I've yet to buy a thermometer to check the dash readout but the readings seem a tad high.

On a bitterly cold morning the other day it was reading 12 Degrees C, when it felt more like 4 or 5..

On a related note, is it the small pointy thing near the fog-lights?

2003 W203 Coupe.

Thanks in advance,
-James

 

[B088IN]

Think mine is optimistic at best on my W208!
I'm sure it thinks it's on holiday even though there is ice all over it

 

[jefrs]

Mine seems to be very accurate. I suspect it is a platinum resistance bulb, which are more accurate than a thermocouple. But there seems to be a small control unit behind it, and that may be adjustable and need calibrating.

 

[andy27168]

Hi,
On a w202, 208, 210, 124, possibly more there is no control unit behind the sensor, it is just a cable that goes straight from the dash cluster out of the cabin under the bonnet to behind the bumper and yes they are generally accurate, if you start getting inaccurate readings from the gauge replace the sensor in the first instance IIRC £8-10, the more wildly inaccuratly the gauge reads the more likely it is to be the sensor faulty.
I have heard that there is a "Hall Effect sensor" which plugs into the back of the cluster which is meant to make allowances for the effect the engine heat etc could have on the sensor.

 

[BlackC55]

I have seen one at 55Deg. It was accurate too.

 

[jefrs]

A Hall effect sensor detects magnetic fields, was used in breaker-less distributors.
Not sure what that would do ;-)

It is possible to use a second sensor to subtract a portion of one temperature from another.

The "control unit" on mine may be a junction box connectiod, possibly to extend standard loom to spoiler.