When an irrigation system does not work properly it is often thought that the culprit is the control unit but it is better to do electrical checks to understand the true causes.
There are two tests: one hydraulic and one electric.
The hydraulic test consists of verifying that the solenoid valves open and close manually using the physical control without current. Some solenoid valves like the Toro have a pin to move, for others like the Rain Bird just rotate the solenoid.
If you find the problem already now intervene on the solenoid valve by watching the video Solenoid valve that you find at this link or check that the water arrives correctly by checking the pump or aqueduct and that all the supply valves are open.
At this point, if the hydraulic part responds correctly, it is necessary to deepen the electrical part starting from upstream (the water source) and arriving downstream (the solenoid valves).
First thing to do, if we talk about control units in 230/24v, is to verify, using a tester, that the transformer works correctly, that is, that it delivers 24/29 volts (I recommend a professional if you do not know how to do it). Once the correct voltage has been found, we move on to the test of the zones by placing the tester in alternating current and starting the control unit in manual cycle mode. At this point one tip will go on the municipality and the other on the sector in operation. The current must be about 24/29 volts. If an area does not deliver them, a track could be skipped and then if you have a free area in the control unit use it otherwise unfortunately you have to replace the control unit. However, check if the non-working zone is activated by moving it to another link.
Now if everything is correct you have to follow the cable and get to the solenoid valves. If we know which one does not work then we must also check if the correct current arrives at the incriminated "coil" solenoid by testing the arrival wire.
Done the test then I can try to reverse the solenoid of a solenoid valve that works with that does not work to identify the culprit definitively.
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