Siemens LOGO Expansion Module AM (4-20mA) Doesn't read sensor input

Hi Folks,

I have a Siemens LOGO 12/24RCE and I've attatched the AM (4-20mA) input module and the AM2Q output module. Both modules have the green run LED on. The output module is putting out a 4-20mA signal.

The AM input module doesn't seem to be reading signals from a two wire 4-20mA transducer. I can't get it to display anything.  I disabled all Analogue inputs on the 12/24RCE base module and I used  AI1 and AI2 in the circuit program and set those for 4-20mA sensor input. I have a continuous liquid level transducer with two output leads. I've wired a 24v DC power supply in series with the transducer and inputs on the module. I've tried changing the gain and nothing I do seems to make the expansion module read the 4-20 signal. I have a bar graph displaying the analog signal amplifiers output. The value stays at 0 even when I move the float up and down on the continuous liquid level float transducer.

Can anyone tell me what I'm doing wrong?

Thanks

Yes Its a "Madison Company " C-series continuous level sensor- Float type. Model # C4651 with a two wire  4-20 mA output. It mentions wiring the + lead of the sensor to the + power supply terminal and then the black - lead of the sensor to the input of an ammeter and then the other terminal of the meter to the - power supply terminal.

I've re-checked my wiring and the settings in the program and it will not display a value. 

I've confirmed that the float is working. I hooked it up to a 24VDC supply set for 500mA and wired a DMM set for the mA range. I get the full 4-20mA range and it changes on the DMM as I move the float up and down.

On the siemens logo the AI is fed directly to an analog amplifier and then I'm attempting to read the output from that block on the display. Should I be using any particular settings? I also was powering both the LOGO, AM2, AM2Q, and Siemens HMI  using 24VDC current limited to 500mA. Is it possible that the current limit is to low? 

If I connect the sensor in series with the AM2 module and the meter I get a few mA displayed. If I disconnect M2 from the -Vdc supply and place my meters positive lead on I2 and then the meters -lead on the -vdc rail I get 4-20mA . 

I don't get it. why isn't the AM2 module reading the 4-20mA signal?