System Won't Start: Controller, Wiring, or Valve Diagnosis

When nothing runs automatically or manually—but valves work manually at the solenoid—the fault is in the control circuit: controller output, field wiring, or solenoids. Check in this order.

Step 1: Verify Controller Power & Output

• Display on? If blank, check 120 VAC supply, transformer, 9 V battery.
• Measure 24–28 VAC at controller terminal strip (C to zone 1) during manual activation.
• No voltage = controller failed. Voltage present = proceed to wiring.

Step 2: Check Field Wiring Continuity

1. Disconnect common and zone wires at controller.
2. At valve box, twist common + zone 1 wires together.
3. At controller, measure resistance between C and zone 1 terminals.
4. Should read <5 Ω (wire resistance only). High/open = cut wire.

Step 3: Test Solenoids at Valve

• Measure resistance across each solenoid: 20–60 Ω good.
• If solenoid tests good but valve doesn't open with controller voltage: diaphragm issue.
• If solenoid open/shorted: replace solenoid.

Step 4: Check Controller Fuse

Some controllers have a replaceable fuse (glass or PTC). If blown, replace and test. If it blows again, you have a field short (see Step 2).

Rain Sensor Check

You mentioned rain sensor is "off." Verify: sensor switch on controller set to "bypass" or "off," not "active." Some sensors have a manual override spindle—ensure it's not engaged.

Quick Isolation

If one zone works manually at controller but others don't, compare wiring. The working zone proves controller output and common wire are good. Focus on the non-working zones' hot wires and solenoids.