I've got a McQuay RDT050CSY that the O/A vanes won't open or close like they should. All the settings are like they should be ( enthalpy, temp., %, mix. etc.)Control voltage on OBA is 5.0V dc, but, will not execute comand to change vane position. (I believe this system uses reverse logic) it doesn't open the circuit to the relays (OB7 & OB8). I have checked this operation on the other units and they work fine. Vane actuator (#3) works fine, it can be controled by jumping the wires together. Also noted LED indicator lights on this board and one on another RTU are very dim, however could not locate any grounding problem. Ya'll got any ideas?