Question
I have an old 446PR Hybrid Irrigation Controller which has always worked well. Recently I have found that it will noy open any of the eight control valves and will not open any in Manual selection either.The clock and pause switches still show up on the screen
My unit has a built in Transformer could that unit be the problem?
All zones were working recently but now none of them open even in manual selection

Answer
Hi David

Two reasons:

1- The controller isn't sending 24V to the valves. If you can measure the volts at the controller terminals. With a volt meter, turn on one zone, put the black lead at the C terminal, white wire, and the red lead at the zone terminal, it should give a reading of at least 24V. If not the controller is damaged.

2- Check the white wire, should be connected to the C port, common, and to ALL, valves. If digging has recently done, check all the wires path from the controller to the valves.

Regards
Guillermo