Troubleshooting Sprinkler System Error Codes After Plumbing Work

After a plumber serviced your hot water heater, your 30-year-old sprinkler system stopped working—even manually—and displays codes like 1A06 and 5A02. Don't panic; this is a common issue with a straightforward fix.

What Those Codes Mean

The codes 1A06 and 5A02 aren't error messages at all. They simply indicate Station 1 on Program A set for 6 minutes and Station 5 on Program A set for 2 minutes. Your controller is functioning normally; the problem lies elsewhere.

First Thing to Check: The Main Valve

Before diving into electrical tests, verify the plumber didn't shut off the main water supply valve to the irrigation system and forget to turn it back on. This happens more often than you'd think.

Testing the Controller Output

If the water is on, test the controller's voltage output to confirm it's sending power to the valves:

1. Manually activate Station 1 from the controller.
2. Set a multimeter to AC voltage (200V range).
3. Place the positive (red) lead on the terminal marked "1" and the negative (black) lead on the "C" (common) terminal.
4. A healthy reading falls between 22–26 VAC.

If you get 22–26 VAC, the controller is fine—the issue is in the valve or wiring. If voltage is low or absent, the controller needs replacement.

Recommended Replacement Controller

If replacement is necessary, the Irritrol Rain Dial series is a reliable, easy-to-program choice that professionals trust. It's a direct upgrade for older systems and offers long-term durability.

Start with the main valve check—it's the most likely culprit and the easiest to fix. Good luck!