Why Is Sonoff Motion Sensor Missing Nighttime Motion Events?

Problem Description

Your SONOFF SNZB-03 motion sensor works reliably during the day but misses motion events at night — lights do not turn on when you walk through a room, or automations do not fire. PIR sensors detect heat differential against the ambient temperature, so warm rooms at night reduce sensitivity. The 60-second cooldown period also causes missed events when you walk through a zone shortly after a previous detection.

Why This Happens in Real Homes

The SNZB-03 is a PIR sensor that detects body heat, so it works in complete darkness — it doesn't need light to see motion. So "missing nighttime motion" usually isn't the sensor being blind; it's more often an automation gated by a light-level or time condition that isn't matching, the re-trigger cooldown, or cold reducing the PIR's sensitivity at night.

First check the automation the sensor drives — if an "only when dark" or time condition is set wrong, the sensor may be detecting motion but the action never fires. Account for the cooldown between triggers and colder nights slightly dulling PIR response. Then confirm the battery is good and the Zigbee mesh is strong so reports reach the bridge. Repositioning for full coverage rounds it out; the sensor itself sees fine in the dark.

Symptoms

• Misses motion at night
• Works by day, misses at night
• Nighttime events not detected
• No triggers overnight
• Motion missed in the dark
• Inconsistent at night
• Detection fails at night only
• Nighttime automations don't fire

Recognize these? Here's what usually causes it.

Common Causes

• Automation gated by a light-level/daylight condition
• Cooldown missing quick successive motion
• Cold night reducing PIR sensitivity
• Low battery worsening at night
• Weak mesh dropping reports
• Automation misconfigured for night
• Sensor placement/coverage
• Firmware issue

Tools & Requirements

Step-by-Step Solution

1

Understand the PIR cooldown period

The SONOFF SNZB-03 motion sensor has a cooldown period after each detection — approximately 60 seconds on the standard SNZB-03, configurable down to 10 seconds on the SNZB-03P. During cooldown, the sensor ignores all motion. If you walk through the detection zone at 11 PM, the sensor triggers. If you walk through again 30 seconds later, it does not trigger because it is still in cooldown. This is not a nighttime-specific problem — it happens 24/7, but is more noticeable at night when you expect every movement to trigger lights.

2

Check for temperature-related sensitivity drops

PIR sensors detect motion by sensing changes in infrared (heat) radiation. At night, if the ambient temperature drops close to body temperature (around 35-37°C / 95-98°F in hot climates, or in rooms with a space heater near the sensor): the sensor cannot distinguish your body heat from the background. The temperature differential drops and motion events are missed. This is not a bug — it is a physical limitation of PIR technology. In summer with AC, the sensor works well because the room is cool (making body heat stand out). In a warm bedroom: move the sensor away from heat sources.

3

Verify the sensor is not obstructed

At night, you may rearrange furniture, close curtains, or move objects that were not blocking the sensor during the day. The SNZB-03 has a 110° detection angle and about 6 meters range. Check the sensor's field of view from its mounted position: anything within 1 meter of the sensor that blocks the PIR lens (a curtain, a tall plant, a chair) creates a dead zone. Also check: if the sensor is behind glass (mounted inside a display case or behind a window): PIR cannot detect motion through glass because glass blocks infrared radiation.

4

Check the battery level

Battery-powered Zigbee sensors reduce their transmission power and wake frequency as the battery drops. A sensor with 15% battery may still detect motion but fail to transmit the event reliably. In eWeLink > bridge > Sub-devices > SNZB-03: check the battery percentage. Replace the CR2450 battery (SNZB-03) or CR2477 (SNZB-03P) if below 20%. After replacing, the sensor sends a check-in event — confirm it shows as online in eWeLink.

Needed for this step

EBL Pack of 8 AA Batteries 2800mAh High Capacit...

This helps complete the fix you are currently reading.

$9.99

View Needed Item

5

Check the Zigbee network for nighttime interference

Some home devices create 2.4GHz interference specifically at night: baby monitors, wireless security cameras that switch to night mode with different encoding, or WiFi-connected devices that run scheduled backups or updates. If motion events are missed specifically between midnight and 6 AM: check what other wireless devices activate during those hours. Also check: some Zigbee routers (smart plugs used as repeaters) may go into a low-power state at night if they are on a circuit controlled by a timer — losing a router disconnects any sensors that used it as a relay.

Quick Solutions

Still having issues? This is usually the deeper cause below.

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.