Testing a Rain Jet RJC Four Timer: Fuse, Transformer, Zone Output

If your 20-year-old Rain Jet RJC Four won't start manually, systematically test power path:

Step-by-Step Tests

1. Fuse: Remove, hold to light — broken filament = replace.
2. Transformer: Measure at terminals marked "T" → should read 24 VAC.
3. Zone Output: Turn on Zone 1, measure at terminal 1 and "C" (common) → 24 VAC. Repeat for each zone.

Interpretation

• No 24V at "T" → transformer bad.
• 24V at "T" but not at zone terminals → controller board failed.
• 24V at zone terminals but valve doesn't operate → field wiring or valve issue.

Note

Rain Jet is obsolete. Consider upgrading to a modern controller (Rain Bird ESP, Hunter Pro-C) when this fails.