W126 - Ambient Temperature Sensor Installation on a 300SD car
 

Hi All;

New to this forum and trying to navigate this section. Here is my information:

Original car is a 1982 - 300SD - OM671

I upgraded my cluster to hold a temp sensor. My old cluster for a 1982 - 300sd did not have that feature so now I would like to add it.

I got a new cluster for my 1982 300sd with part number 126 542 44 01
And a VDO temp sensor with part number 316 202/3/1

It requires a 4 pin connector in the back of the VDO temp sensor. Of course my car did not have that.

My question is if anyone has this temp harness sensor laying around?

How do I connect the MB Ambient temp sensor to the unit? I got this MB part MER-0015422618 from FCP.

Since my temp sensor is in celsius, and has a 4 pin connector, do I need to look elsewhere for parts/harness/temp connector? I have seen 5 pin temp sensors as well. Even those can be hard to connect.

I know the peachpart forums have some write ups as well but that is occasionally hard to navigate.

Any information/bashing/discussion is welcome!

Thanks

I know member jay_bob rewired his temp sensor to work with more functionality, his threads may have a writeup.
Or maybe send him a pm asking about details.

Wow I haven't been on the forum in forever... got an email last night.

If you have the 4-pin display you will need the matching 4 pin harness connector.

These were the earlier generation that did not have the vehicle speed compensation.

Later generation displays did have the compensation hence the extra pin. There was a vehicle speed signal (at least in the 124s) that was derived from the speedometer and was used for the cruise control, climate control, and the outside temperature in later 124s.

F vs C is determined by the display electronics not the sensor.

The display should read low scale for open circuit (negative 30s) and high scale for short circuit (120s) on the sensor. The sensor probe is just a variable resistor (PTC Thermistor).

found the old post I made with the pinout from 11 years ago!

These are the display head pin roles and where they went on the 124. These connections may be different in the 126, but the functions of the display pins should be the same.

pin 1 - blk-red - power from F6
pin 2 - brown - ground from W1
pin 3 - green - sensor
pin 4 - gry-blu - dash lights from X6/1

The way they did it on the 124 was the sensor was furnished with a molded cable and a connector. The connector lived in the bottom of the fuse box and mated to another 2 pin connector that went to the display. No connections to the fuse box, just used the bottom of the fuse box (the spaghetti pot!) as a home out of the weather. The sensor connects between the sensor pin and ground. This was done in the harness going to the display.

Hope this helps