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Hi Everyone


Hope you are all well.


I am busy working on a mercedes engine using its PLD and ADM to communicate with it.

The ADM on the vehicle give you outputs for oil pressure and coolant temprature etc.


I have set my analog input to 0-10v and it is wired to receive a positive signal from the ADM.

It does pick up a coolant temp but immediately goes back down to 0 value.


When i take a VDO guage for temprature, it picks up the proper temprature and remains contant.


I have also tried to set the analog input to 0-20m/a aswell as 4-20 m/a,.

But it does the same thing.


Is there something im doing wrong with the input as i know signal is coming through since the VDO guage works.

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  • MVP 2014

Do you have a specification for the analogue outputs of the ADM (or the inputs on the VDO gauge)?  Automotive signals don't usually play by the same rules as industrial signals.


I would also try to measure the signal with a multimeter, starting on the voltage range.

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  • MVP 2023

Have you put a scope on the signal to see what happens when you connect the VDO gage vs the PLC?

Which analog module are you using?

What is the input impedance of the VDO?  

Could it be because the PLC analog input is common grounded and the VDO is floating or tied to the vehicle?  

Have you tied the PLC power supply common to the vehicle ground?


Joe T.

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I have ground the ADM/PLD to a common 12v. As the VDO guage is grounded to that when i was testing.

The PLC is grounded to a 24v ground as the ADM/PLD are working on a 12v system.


Specifications for Outputs from ADM


Pin 12/3
Oil Pressure 


Pin 12/04
Coolant Temp


Imax - 120 mA

Umax - Ub

Umin - 0v


A) analog low side driver oil pressure guage, short protected

B) low side switch for warning lamp


Do not have a scope to test unfortunately.

Using the V200-18-E46B snap-on

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