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Irritrol RD-900-EXT Controller Panel Failure: Chattering Solenoids and Display Glitches

When an Irritrol RD-900-EXT chatters solenoids in auto mode, fails in manual/semi-auto, and the display flutters, the controller panel (facepack) has failed—not the wiring or valves.

Why It's the Panel

Chattering = rapid on/off switching from faulty output driver
Display flutter = microprocessor or display driver instability
Manual mode failure = panel button/switch matrix or logic fault
Transformer tests good (24VAC) = power supply OK

Fix: Replace the Panel Only

Open controller cabinet.
Unplug the ribbon cable connecting panel to base.
Pull panel straight out from plastic hinge pins.
Buy replacement panel (~$85–$100) from irrigation supplier (Ewing, John Deere, SiteOne).
Install new panel, reconnect ribbon, test.

Quick Check First

Replace the 9V backup battery (top compartment). A weak battery can cause erratic behavior on RD-900 series. If that doesn't fix it, the panel is done.

Don't replace the whole controller—the base and terminal board are fine. Panel swap takes 5 minutes.

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