Rain Bird RC-7Bi: Zone 3 Valve Won't Open, Pump Dead-Heads and Blows Fittings

System quit. Dealer replaced clutch ($89), then transformer ($46). Bypassed house wiring → worked. Fixed blown house wire connection. Now zone 3 blows fuse, pump builds back-pressure, blows 2" connector apart. Suspects valve/solenoid causing water backup.

Dead-Head Diagnosis

Tony: "It sounds like the valve for zone 3 is not opening and the pump is working against 'dead head'... the pump is pushing water against a valve that isn't opening when it is programmed to and creating a troublesome situation."

Electrical Testing Procedure

Detailed volt/ohm testing for zone 3 circuit:

1. Controller output: 24-27 VAC at COM and zone 3 terminal.
2. If voltage good, ohm-test field wiring (solenoid ~30 ohms normal; 6-8 = short).
3. Disconnect at valve to isolate solenoid vs. wire short.
4. Check wire resistance alone (few ohms).

Fuse blowing on zone 3 indicates a short in that circuit (solenoid or wiring). The pump blowing fittings confirms the valve isn't opening to relieve pressure.