W124 outside temp display fault

[Deleted member 11979]

Evening,

The outside temperature gauge on my W124 has a fault.

When you initially switch on the ignition, for a second or so, the gauge displays the correct temperature, then drops by around 10 degrees.

It will still fluctuate correctly registering changes up and down by half a degree or such as the day progresses, but always around 10 degrees too cold.

Turning the car on and off does not sort the problem out, unless it's left for an hour or so, hen it will initially show the correct temperature again for a second or so.

Sensor, display or something else?

Any ideas greatly appreciated.

 

[balge]

Exploring the VDO Outside Temperature Display in a W124 - PeachParts Mercedes ShopForum

Might be of use?
cheers

 

[bing]

If it's fluctuating it's the sensor. If the LCD is blank or goes on/off with the correct temp, then it's the LCD display itself - which is about £300 from MB But plenty from breakers for about 50quid

 

[Deleted member 11979]

Thank you, all roads point to sensor, before I replace could a weak earth or anything else silly do it?

 

[DanSLC]

There is a connector joint in the cable from the sensor to the display beneath the tray of fuses in the fusebox. It's a 2-pin connector, brown and green wires I think. You could check there is no dampness or corrosion on that first.

You can also check correct operation of the display and sensor at this point. Unplug the joint and use a multimeter at the across the wires coming from the sensor - there should be a steady reading of 3 kOhms at 25 deg C ambient, becoming higher as the temperature drops.

If you have a 3kOhm resistor then place that across the wires to the display - it should ready a steady 25 deg C for that value of resistor.

By doing those two tests you can positively identify whether it's the sensor or the display.

Hope that helps!

Dan

 

[coupe deville]

Fuses , have you replaced all the fuses lately and cleaned the fuse holders ?