Sensor Flushometer Won’t Flush: Power, Sensor, and Valve Checks
Automatic flush valves fail at four basic points: power, sensor detection, actuator or solenoid operation, and water supply. Check them in that order before replacing parts.
Likely causes
Do not jump straight to the most expensive possibility. These are the common places to start:
- Dead batteries or lost power
- Dirty or blocked sensor
- Closed control stop
- Failed solenoid or actuator
- Incorrect sensor setup
| Possible cause | How to check | Routine first move |
|---|---|---|
| Dead batteries or lost power | Identify model and power type | Restore power |
| Dirty or blocked sensor | Clean the sensor window | Clean or recalibrate sensor per manual |
| Closed control stop | Replace batteries as a complete set | Replace model-correct batteries |
| Failed solenoid or actuator | Verify the control stop is open | Service the solenoid only after supply and sensing are proven |
| Incorrect sensor setup | Use the manufacturer reset or manual override | Restore power |
Tools and preparation
Bring these
- Flashlight
- Rags or towels
- Basic hand tools appropriate to the fixture
- Correct manufacturer repair parts when needed
Before touching anything
- Confirm the exact location and complaint.
- Photograph labels, settings, fault codes, and the original condition.
- Determine whether the failure affects one item or several nearby items.
- Know how to safely isolate the system if the task requires it.
Step-by-step checks
Identify model and power type
Work through this check deliberately and record what you find before moving to the next one.
Clean the sensor window
Work through this check deliberately and record what you find before moving to the next one.
Replace batteries as a complete set
Work through this check deliberately and record what you find before moving to the next one.
Verify the control stop is open
Work through this check deliberately and record what you find before moving to the next one.
Use the manufacturer reset or manual override
Work through this check deliberately and record what you find before moving to the next one.
Routine fixes that make sense here
- Restore power
- Clean or recalibrate sensor per manual
- Replace model-correct batteries
- Service the solenoid only after supply and sensing are proven
Common mistakes
- Replacing parts before proving the failure.
- Changing several settings or components at once.
- Failing to photograph the original condition.
- Ignoring whether nearby equipment has the same symptom.
- Crossing into electrical, refrigerant, life-safety, structural, or plumbing work beyond training.
Sensor-valve troubleshooting shortcut
Separate the problem into four layers: power → sensing → actuator/solenoid → water. If the sensor indicates detection but the valve does not move water, stop spending time on range settings and move downstream to actuator and supply checks.
When to stop and hand it off
- Hardwired electrical diagnosis is required
- Water cannot be isolated
- Electronics are wet or corroded
Frequently asked questions
What should I check first?
Start by deciding whether the problem is local to one fixture or piece of equipment. Then begin with the simplest safe observation: identify model and power type.
What is the most common mistake?
Replacing parts before proving the failure. BuildingWrench recommends documenting the symptom, changing one thing at a time, and testing after each change.
When should maintenance stop?
Stop when the repair crosses your training or site-safety boundary. In this case, one clear handoff point is: hardwired electrical diagnosis is required.
What should I document?
Record the exact location, model or asset tag, what the equipment was doing, what you checked, what you changed, and whether the fix held through repeated testing.
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BuildingWrench provides general educational information for commercial-facility maintenance. Manufacturer instructions, applicable codes, site procedures, and required trade qualifications always take priority.