The solenoid is the small electrical part on top of a sprinkler valve that opens and closes it when the controller sends a signal.
When a solenoid fails, the valve may not open at all, or it may stick open.
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Quick Answer
A bad sprinkler solenoid usually shows up as a zone that won’t turn on even though the controller shows it running, or a valve that won’t close. Causes include burned-out coils, stuck plungers, corrosion and surge damage. A technician confirms a bad solenoid with a resistance test, and replacement is usually straightforward.
What You May Be Seeing
- Zone won’t turn on when the controller runs it
- Zone opens manually but not automatically
- Zone won’t shut off
- Zone works intermittently
- Water leaking around the solenoid
The solenoid opens the valve by moving a plunger. If the coil fails electrically or the plunger sticks, the valve can’t respond to the controller.
The First Question to Ask
Does the zone open when the valve is operated manually?
If the zone runs manually but not from the controller, the solenoid or wiring is likely the problem. If it won’t run manually either, the valve itself may be at fault.
If the Valve Won’t Open From the Controller
The solenoid or its wiring may have failed.
Common causes include:
- Burned-out coil: fails resistance testing
- Stuck plunger: debris or corrosion
- Wiring problem: field or common wire
If the Valve Won’t Close
The solenoid may be stuck open.
Common causes include:
- Stuck plunger: holds the valve open
- Debris: in the solenoid port
- Loose solenoid: not seated properly
After a Storm
Surges can burn out solenoid coils.
Water Leaking Around the Solenoid
A loose or damaged solenoid can leak and may need to be reseated or replaced.
The Zone Works Sometimes
An intermittent solenoid or a corroded splice can cause on-and-off operation.
What You Can Check Yourself
- Confirm the zone is programmed
- Note whether the zone runs when started manually from the controller
- Look in the valve box for damage or leaking (look only)
- Note whether the problem started after a storm
What a Technician May Test
- Solenoid resistance (ohm) test
- Station output test
- Manual valve operation
- Wire and splice inspection
Most Common Causes
- Burned-out solenoid coil
- Stuck plunger
- Corrosion
- Surge damage
- Loose or damaged solenoid
Repair or Replace?
A failed solenoid is usually replaced on its own without replacing the whole valve. If the valve is also worn or cracked, replacing the valve may make more sense.
When to Call a Sprinkler Professional
Call a professional if:
- The zone opens manually but not from the controller
- Electrical testing is needed
- Several solenoids failed after a storm
- The solenoid is leaking
Find a sprinkler repair pro or read our emergency shutoff guide if water won’t stop.
Related Sprinkler Problems
- Why Won’t My Sprinkler Zone Turn On?
- Why Won’t My Sprinkler Valve Open?
- Why Won’t My Sprinkler Valve Close?
- How Do I Know If My Sprinkler Common Wire Is Bad?
Related Repairs
Typical Repair Cost
What you pay depends on the cause, the parts and your area. See our Sprinkler Solenoid Replacement Cost Guide for typical ranges. Prices vary, and only an on-site diagnosis can give you an actual quote.
Frequently Asked Questions
How do I know if my sprinkler solenoid is bad?
A technician tests its electrical resistance and checks whether the valve opens manually.
Can a bad solenoid keep a zone running?
Yes. A stuck plunger can hold the valve open.
Can I replace just the solenoid?
Usually, yes. Solenoids are typically replaced separately from the valve.
What causes solenoids to fail?
Age, corrosion, debris and electrical surges are common causes.
Bottom Line
A bad solenoid can keep a valve from opening or closing. Testing confirms whether the solenoid, wiring or valve is the problem.
Replacing a failed solenoid is usually a targeted repair.
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