James Hardie RD-600 Kills Batteries: Bad Transformer Diagnosis

Controller Drains 9V Battery in Days: Transformer Failure

If your Rain Dial RD-600 (outdoor mount) works briefly on battery but display dies quickly, and you've replaced the battery twice, the 24 VAC transformer is almost certainly dead.

Why This Happens

• Transformer outputs 0 VAC (or very low).
• Controller runs solely on battery backup.
• 9V alkaline cannot power the display + valve solenoids for more than hours.

Test Procedure

1. Set multimeter to AC volts (200 V range). 2. Probe the two controller power input terminals (usually labeled "24VAC" or "TRANS"). 3. Reading should be 24–28 VAC. 4. If < 20 VAC or 0 VAC → transformer bad.

Replacement

• Any 24 VAC, 40 VA transformer works (Rain Bird, Orbit, Hunter, generic).
• Cost: $15–25 at hardware stores or online.
• Mount in weatherproof box if outdoor.

Pro Tip

Before buying, verify the controller itself isn't shorted: disconnect all zone wires, power up transformer, measure voltage at terminals. If voltage holds, controller is fine.