Grab a multimeter Turn
your Multimeter to the proper VAC setting. Turn the problem zone on with the
manual start on the controller. Here we will say it is zone 1. Touch one lead
to the common and one lead to the zone 1 wire/screw. You should get around 24v.
Usually 22 to 28 works. If you get lower than 22 you have a problem.Try two zones. This will tell us if you have power coming from the box to the zones.
Let’s
assume the voltage is good. Now let’s check the wires. We’ll check for
continuity, which is testing the ohms or resistance of the zone. Turn to the
Ohms setting. It might look like (Ω). Check your manual to be sure. This will
test for a short in the circuit. First, turn off the controller. You don’t want
to check resistance with a live circuit. Disconnect the zone wire. Place one lead on the common terminal
and one lead on the zone wire. Depending on the valve brand you should
get a reading from 20-60 ohms; every manufacture’s valves will have a slightly
different reading. Low signals indicate trouble with the solenoid. On the other
hand, any reading above 60 means you have a wiring problem, either stripped
insulation, nicked wire or bad connection.