[W126 Coupe] Outside Temperature Display Wiring Question

[Dick Spellman]

Hi Clay:

I have the following wire harness off of the 86 300SE temp gauge that I 
repaired a few years ago after it suffered an electrical fire caused by 
the blower motor fuse super-heating the sensor cable and causing a dead 
short.

Anyway, here is what I have:

The Temp gauge at the back of the instrument cluster (IC) has five (5) 
pins looking at the back of the IC you will have:
-top left pin =  #4;  a solid black heavy single conductor lead from the 
original harness -not sure where this goes

 top right pin =  #3; Positive lead from temp sensor bulb under the 
front bumper

 lower left pin =  #2 (GROUND)  with one lead to (-) temp sensor bulb 
negative and a second lead to to ground post behind the IC.  There are 
several ground posts stacked vertical, it does not matter which post you 
place your spade loop on.

 lower center = not used;

 lower right pin =  #1. Black/red lead form the original harness - not 
sure where this goes

Now I rewired the 'fried' harness (MB Part #126-540-7808) and it's 
respective IC/temp gauge connector (MB part #010 545 7028) some time 
ago.  Everything is working properly in the 86 300SE.  I need to take a 
volt meter and confirm the polarity and or use of the two mystery lead 
(#'s 1 & 4) so you can complete the harness wiring.  I'll try and get to 
this later today.  If you work things out in the meantime, I sure would 
appreciate your results and a confirmation of the two mystery leads.   
Wishing I had taken notes when I did this the first time.

Regards,

Dick

Clay Woodward wrote:

> I am in process of trying to install an outside temp Display in my 83 
> 500 sec and have a question on the wiring.
>  
> There are four different colored wires coming from the plug in the 
> back of the display unit They are
> (clockwise from the left top looking at the back of the unit)
>  
> Grey/Blue
> Green
> Purple/Black
> Brown <--(2 wires here)
>  
> I got these colors from a 1986 year car.
>  
> I also have the thermometer and the wiring it came with has 2 leads at 
> the end.
>  
> Can anyone help me with this wiring??
>  
> Thank you,
>  
> Clay Woodward
>
>
>  
>
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