Why Is Sonoff Motion Sensor Triggering False Events?
- Heat sources in view (HVAC vents, radiators)
- Direct sunlight or moving shadows
- Pets in the detection field
Problem Description
Your SONOFF SNZB-03 motion sensor triggers when no one is in the room — lights turn on by themselves, phantom motion events appear in the log. PIR sensors detect changes in infrared radiation, so HVAC vents, sunlight beams through blinds, pet movement, and car headlights through windows all create heat signatures that trigger false detections.
Why This Happens in Real Homes
SONOFF SNZB-03 false triggers come from the nature of PIR sensing — it detects moving heat, so anything that moves warm air or heat across its field can trip it: an HVAC vent or radiator blowing, sunlight and moving shadows through a window, or pets. It's not detecting people, but it is detecting real heat movement.
Aim the sensor away from HVAC vents, radiators, and AC units, and keep direct sunlight and windows out of its field of view, since moving air and sun-driven temperature changes are the top false-trigger sources. Mount it higher and angled down to reduce pet triggers if you have animals. Repositioning away from heat sources and reflective surfaces resolves the large majority of false events; keep firmware current.
Symptoms
- False motion triggers
- Triggers with no one there
- Random motion events
- Triggers on pets
- False alerts
- Motion detected falsely
- Too many triggers
- Nuisance detections
Recognize these? Here's what usually causes it.
Common Causes
- Heat sources in view (HVAC vents, radiators)
- Direct sunlight or moving shadows
- Pets in the detection field
- Reflective surfaces / moving heat
- Sensor aimed at a heat/AC source
- Placement facing a window
- Rapid temperature changes
- Firmware/sensitivity
Most fixes happen in the first 3 steps.
Do not overcomplicate automation before correcting physical placement.
Tools & Requirements
Step-by-Step Solution
Identify common PIR false trigger sources
The SONOFF SNZB-03 uses a passive infrared (PIR) sensor that detects changes in heat radiation. False triggers come from: pets walking through the detection zone, heating/cooling vents blowing warm or cold air across the sensor's field of view, sunlight beams moving across a surface (especially through venetian blinds — the moving shadow/light pattern creates alternating heat signatures), and car headlights through windows at night. Identify which of these exists near your sensor and address the specific source.
Reposition the sensor to avoid heat sources
Mount the SNZB-03 away from HVAC vents (at least 2 meters), away from windows that get direct sunlight, and at a height where pet movement is below the detection zone. The SNZB-03 detection cone starts at the lens and expands outward at 110°. Mounting it at 2.1-2.3 meters height and angling it slightly downward gives the best human coverage while minimizing pet triggers (for cats/small dogs). Large dogs will still trigger at this height. For rooms with persistent false triggers from sunlight: mount the sensor on the wall facing away from windows.
Adjust sensitivity on the SNZB-03P
The newer SNZB-03P has adjustable sensitivity: Low, Medium, High. In eWeLink > bridge > Sub-devices > SNZB-03P > Settings. Set to Low in areas with known false trigger sources — Low sensitivity requires a larger heat differential to trigger, filtering out small sources like air currents or distant pet movement. The original SNZB-03 does not have adjustable sensitivity — if false triggers persist with the original model, repositioning or adding a detection mask is the only option.
Add a detection mask if repositioning is not possible
If you cannot move the sensor and false triggers come from a specific direction (a window, a vent): you can partially mask the PIR lens to narrow the detection zone. Place a small piece of electrical tape over the portion of the lens facing the false trigger source. This blocks infrared from that direction without affecting detection in the remaining field of view. Start by covering a quarter of the lens on the problematic side and test — adjust coverage until false triggers stop while legitimate motion is still detected.
Check for firmware-related trigger bugs
Some early SNZB-03 firmware versions had a bug where the sensor sent a false 'motion detected' event immediately after a battery check-in (every 60 minutes). SONOFF fixed this in firmware updates. Check your sensor firmware through the Zigbee Bridge: if the bridge can update sub-device firmware, apply any available update. If not: check the SONOFF community forum for the latest SNZB-03 firmware and whether your bridge model supports pushing it. The SNZB-03P (newer model) does not have this bug.
Quick Solutions
Still having issues? This is usually the deeper cause below.
If the sensor still misses events after repositioning, check whether a scheduled 'home' or 'away' mode is overriding the sensitivity setting silently.
Sensor placement quality often matters more than automation complexity.
This issue almost always looks more complex than it is — the majority of cases trace back to a single setting, a stale credential, or a default that shipped wrong.
- Heat sources in view (HVAC vents, radiators)
- Direct sunlight or moving shadows
- Pets in the detection field
- Reflective surfaces / moving heat
- Sensor aimed at a heat/AC source
Before you go — try one of these (they fix most cases).
Most popular upgrades chosen by Sonoff False Motion Alerts owners.
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Official Manufacturer Manual
SONOFF provides official product documentation through their online manual rather than downloadable PDF. Access setup guides, troubleshooting steps, and product specifications for your Sonoff False Motion Alerts.
Source: sonoff.tech
Need More Help? SONOFF Support
Note: The contact information below connects you directly to SONOFF's official customer support team, not Trunetto. They can help with warranty claims, device replacements, and advanced technical issues.
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