Do you have a 10K potentiometer? If you do try to connect one side arm to the +5V, another side arm to the 0V, and the center arm to the ADC #2 (pin 7).
Write the simplest program to read the ADC every second.
E.g.
Clk:0.5s Fn1
|---||----------------{dCusF}
Inside function Fn1:
FOR I = 1 to 8
DM = ADC(I)
NEXT
This ensures that all 8 ADC channels are read. Go to online monitoring and check the ADC readings on the "View Variable" screen. Now turn the potentiometer so that the voltage applied to the ADC varies and see which ADC channel is working.
Another test would be connect a cable from the analog ground (0V) to each ADC input one at a time and see if the online monitoring screen shows that the corresponding ADC channels reads zero.
If the ADC still does not produce correct result with the above tests then your PLC's ADC port may be damaged and please arrange for an RMA.
