FX3S contacts not energizing

[chris76 0]

I replaced an old FXo PLC with a FX3S. Everything seemed great until I was checking to make sure the valves open on the PLC command. I find that the lights on the PLC turn on and off as you would expect but for some reason the contacts are not energizing and sending the open signal to the valve. The light shows an energizing condition but when I measure the voltage at the output I'm not getting anything. This is happening for outputs that are powered by COM3. I verified that we have 24VDC at COM3 so I am not sure why the outputs are not energizing. Could this be an internal defect in the PLC? thanks in advance Edited 17 Oct 2013 by chris76

[Bryll 31]

Have you checked that you supply the common supply for the outputs? Some of the systems has one common supply for 4 to 6 outputs, and some has separate supplies for each of the outputs. I've been there myself

[Inntele 60]

Unlikely it a manufacturing defect of the PLC. 1) It's not a good idea to control the valve by PLC output directly. It can be done just in case if the valve is very low power (my recommendation is no more than 200mA). In other case the valve should be controlled through the intermediate relay. 2) The snubber diode has to shunt the load. If it is not done, likely the contact circuit of the output relay has been destroyed.

[chris76 0]

Yes sorry I forgot to mention that the PLC output goes to a solenoid valve that actuatlly actuates the valve.

[Inntele 60]

Of course, I also have meant a solenoid valve, however it could be a different power.