Do you have wire diagram for the connector? Thanks!

Wiring for the 4 to 5 pin connector
 

I sell many outside temp displays on Ebay and occasionally come across an individual that needs to convert from a 4 pin connector to a 5 pin.
The diagram I found somewhere on this forum indicates as follows:
Wire color position usage
brown 1 ground(and temp sensor ground)
grey/blue 2 circuit 58D from x6/1(illumination)
green 3 temperature sensor(signal)
----- 4 not used
black violet 5 circuit 15 hot(color may vary)

I hope this helps some.
Dan(cdplayer)

Here's a schematic for a late E320.

I measured at the connector:

pin 1: ground, OK
pin 2: nothing when head light is off and instruments backlight is off; 11.98V when turning lights on. OK
pin 3: nothing displayed for sensor signal
pin 4: 12V permanent ??? for what?
pin 5: 12V permanent. OK

The power supply is OK, that means both my display units seem broken, what a bad luck!

Thanks, this time I was looking for my W124 300CE. I saved that info for my other ride E320 for later use.

Sorry I wasn't more clear. That schematic is for a '95 W124 E320.

Texholdem, it looks like same thing happened to me, tested outside sensor with resistor under fuse panel still no temp display. I also tested and got same voltage results to the pins behind the speedometer. I just received my ebay lcd display and it behaves the same as the one on the car. With car running or key in the on position, nothing on display ... they both also only illuminate when i turn on the parking lights etc .... When i first bought the car it would go up to the highest lcd temp + 136 i think, all the way down to the lowest temp, then shutoff ... did this behavior a few weeks and eventually stopped showing anything ... now I believe either both displays are bad, or both lcd displays are good and something else is the issue. Does anyone know would to bench test the display? I am leaning more towards the ebay unit i received is also bad too though .... i didn't check fuse yet, but i remember seeing on another post that the fuse is the same as the one for the turn signal and those work fine ... any suggestions before i have to deal with this ebay guy?

See Jeremy's reply (#2)
 

Thanx, compress ignite i saved the screen shot and will investigate further .... talked to the ebay seller and he said he has another display that he will test 1st then send ... lets see

I'm having the same problem. It happened when I replace my alternator and serpentine belt. The backlight is fine. Earlier today the temperature gauge was reading 136+. So how did you fix the problem.

I gave up after changing two display units without success. Situation exactly like lafooy described.

You possibly damaged the wire from the sensor, which is mounted behind the front license plate.

not sure if what i am about to say is true or not but i'll say it. I am assuming that if the car is running and the outside temp display shows any number clearly, the sensor is the problem. Therefore, if nothing is displaying at all with the car on, the display is the problem.

Back to square one again. Got my 3rd lcd display today and again nothing ... all of this time wasted. going to look into replacing my sensor by the front license plate now. Should have realized it when pin 3 (sensor signal) was not showing any voltage

this update is mostly for texholdem ... i cut off the sensor today by the license plate and i am making progress! now when i go to start the car, display reads -36 for a few seconds and shuts off ... will replace the sensor and update this thread with results