Since my first email, I have collected some more data. I
used a volt meter to measure the current flow through the hot wire to the valve box: 24 volts at the control box and 24 volts at the valve box, a good thing. This means, I believe, that the ground wire is working fine, since I used the ground wire to complete the circuit with the volt meter.
I was able to make all 3 valves function propertly by turning the bleed screw on all the way. So I know that the valves are mechanically sound.
When I turn on any of the 3 valves, I hear the solenoids trying to work. But since all 3 are not turning on, I now believe that all 3 solenoids are defective. So I am going to replace all 3 valves.
I now have (old) Hydrorain valves. Do you know if I can buy replacements valves that are compatible? Then I can just replace the solenoids and top part of the valves, leaving the bottom part of the valves in place. This would be very easy to do and eliminate a lot of work.
Thanks for your help and suggestions.