Question
I recently moved into a new house, that has a RD 900 installed.  I have checked the wiring a few times, all seems OK, the only thing I can think of is that there is nothing hooked to the MV screw, is that why the valves are not responding?

There is no Master Valve wire, but there are 3 wires to that are linked to the solenoids, the common wire and the 24 VAC wires.  The 24 VAC wires have a third wire as well, which is connected to the common wire screw.  Any ideas?

Answer
Hi Tyler

The MV is used only if you have a pump start relay or an electrical back flow preventer.

The connections should be as follows:

The VC wire shuold go to each valve selenoid. white wire.
The numbered ports should have different color wires going to each selenoid.
The 24VAC should only have two wires that comes from the transformer.
If you have any back flow preventer or pump start relay it should be connected to the MV and the white wire to the VC.

If you don't have the manual find one at http://www.coastwaterworks.com/irrigation/irrigation_manuals.htm#richdel

Regards
Guillermo