How to troubleshoot a multimeter

Spring Startup: My Go-To Multimeter Troubleshooting Tips for Irrigation Systems

Winter’s finally backing off, and spring’s creeping in fast. That means it’s time to get ready for irrigation system startups again. Around this time every year, I get the same calls zones not turning on, solenoids acting up, or whole systems refusing to cooperate. It’s not always easy, especially when you’re dealing with a controller or system you’re not familiar with. But over the years, one tool has consistently saved me a lot of frustration: a multimeter.

I’ve been in this field a long time, and whether I’m troubleshooting a simple residential system or working on a complex commercial install, my multimeter is always in my truck. It’s inexpensive, reliable, and it handles everything from checking voltage to diagnosing solenoids, valves, and field wiring issues.

Why You Need a Multimeter on Every Job

There’s no guesswork when I’ve got a multimeter in hand. I use it to test both AC and DC voltage, as well as resistance—especially resistance. Most of the time, that’s the key to figuring out what’s wrong with a system. For instance, I can spot a short or open in seconds, instead of wasting time swapping out solenoids or digging up wires blindly.

Personally, I recommend Armada’s multimeters—they have a few solid options. And if you’re handling landscape lighting too, get one that reads true RMS so you’re covered across the board.

5 Terms I Rely on While Troubleshooting:

  • AC volts (VAC): Most irrigation solenoids run on AC, so this is your go-to for checking standard voltage.

  • DC volts (VDC): Used in battery-powered or specialty systems. Just remember: red is positive (+), black is negative (-).

  • Resistance (ohms Ω): This tells you how hard it is for current to move through the system—think of it like friction in a pipe.

    • Short: Below 20 ohms. Something’s letting too much current through.

    • Open: Over 60 ohms. Not enough current’s getting through.

My Process for Using a Multimeter in the Field

Here’s how I walk through a resistance test when a zone’s not activating:

  1. I disconnect the common wire from the controller’s terminal strip.

  2. I dial in to the resistance setting (Ohms).

  3. One lead touches the common wire, the other goes to each station terminal.

  4. I jot down the resistance readings and compare.

What I’m Looking For:

  • 20–60 ohms? That circuit’s probably good. But I stay alert—it doesn’t rule out valve or controller problems.

  • Below 20? That’s a short. I go out, disconnect the solenoid, and test it solo. If the low reading sticks, it’s time to replace the solenoid.

  • Above 60? That’s an open. Again, I isolate the solenoid to see if it’s the culprit. If not, I know I’ve got a wiring issue.

Quick Tip:

If the solenoid checks out but I’m still getting weird readings, I cut out the wire connectors and twist the station and common wires together right at the valve. Then I retest from the controller. If it reads super low (like under 5 ohms), I’ve found the problem: bad connectors.

What I Do If Resistance Is Still Off

Still getting high resistance even after direct wiring? Then I’m likely dealing with an open or damaged section in the line. That’s where wire tracing gear comes in handy—it’s the only way to pinpoint the exact location without tearing everything up.

To test for shorts to ground, I use this little trick:

  1. I wrap bare wire around a screwdriver and jab it into the ground (wetting the soil helps).

  2. I touch the multimeter leads to the station wires and the common wire one at a time.

  3. I want readings above 700K ohms. Anything below? There’s a nick in the insulation somewhere, and that wire’s grounding out.

Transformer and Controller Checks

Transformers can be a pain, but your multimeter makes it easy. I check the primary and secondary windings the same way—resistance readings mean it’s intact. An open circuit tells me it’s toast.

For battery-powered solid-state controllers, I also use my multimeter to figure out what kind of battery it needs:

  • 0 volts? It takes alkaline.

  • 7–13 volts DC? That’s for rechargeable NiCads.

And just to be clear—don’t swap alkaline and NiCad batteries. It won’t end well.

Final Thoughts

Look, troubleshooting irrigation systems isn’t always cut and dry. Sometimes it’s one issue, sometimes it’s five hiding behind each other. But if there’s one tool that’s helped me cut through the noise again and again, it’s my multimeter. I never head out for spring start-ups without it.

Voltage Vanguard
Author: Voltage Vanguard