Litter Robot 4 lights meaning: every color and what to do
This litter robot 4 lights meaning guide lists every light bar and button pattern from Whisker's official light codes guide. Each row says what the light means and the fix Whisker gives.
Researched by Riley Hart · updated Oct 15, 2026 · How we research
Solid blue means the Litter-Robot 4 is ready. Flashing blue means the drawer is full, solid red means the cat sensor was triggered, red and blue alternating means the curtain sensors are dirty, solid yellow means paused and solid purple means Sleep Mode. Whisker's fix for most faults is to clear the cause, then press Reset and Cycle.
| Light bar pattern | What it means | What to do |
|---|---|---|
| Solid blue | Ready | Nothing. This is the normal status after a Clean cycle. |
| Flashing blue | Drawer full | Empty the drawer, press Reset, then press Cycle. |
| Blue with 2 flashing yellow | Scale triggered for over 30 minutes | Remove excess weight or litter, move the unit off carpet, mats, cords, grout lines and away from walls, press Reset. |
| Blue with 1 flashing yellow by Connect | Onboarding mode, waiting for the app | Finish setup in the Whisker app. |
| Blue with flashing blue by Connect | Connecting or reconnecting to WiFi | Wait for it to connect. |
| Blue with solid white by Connect | WiFi is off | Short press Connect. |
| Blue and purple alternating | LitterHopper motor error | Follow Whisker's LitterHopper support article. |
| Blue and white alternating | Motor connection fault | Secure the motor connection per Whisker's motor guide. |
| Solid red | Cat sensor triggered | The unit cycles after the delay countdown or when you press Reset. |
| Flashing red | Cat or weight detected for over 30 minutes | Check for excess litter or weight, then reset. |
| Red with 2 flashing white | Globe position not detected | Follow Whisker's support article for this code. |
| Red with 2 flashing yellow | Globe jammed or overloaded | The unit retracts and retries. Contact support if it repeats. |
| Red and green alternating | Factory scale calibration lost | Base needs replacing. Submit a support request. |
| Red and blue alternating | Curtain sensors dirty | Clean the three laser sensors. |
| Single red light moving back and forth | Motion detected in the drawer | Check the drawer area. |
| Solid purple | Sleep Mode on | Long press Cycle to toggle Sleep Mode. |
| Brief white flash in the middle | Firmware update over WiFi | Nothing. |
| White with 2 flashing yellow | Wrong power supply, low voltage | Use the correct Whisker power supply. |
| Solid yellow | Paused | Press Cycle or Reset. If it stays paused, power off and on. |
| Flashing yellow | Bonnet removed | Reinstall the bonnet. It resumes 5 seconds later. |
| Single yellow light moving back and forth | Pinch detector activated | Clear anything blocking the globe. |
| Single yellow light moving with the globe | Clean or Empty cycle running | Nothing. |
| Green and white alternating | Anti pinch fault at power up | Follow Whisker's support article for this code. |
| Single green light moving back and forth | Curtain sensors auto calibrating | Nothing. |
| Green with 2 flashing red | Sensor auto calibration failed | Clean the curtain sensors, then run a test cycle. |
Meanings and actions from Whisker's Litter-Robot 4 Light Codes Guide and related support articles, checked October 15, 2026. Solid blue as Ready comes from Whisker's no power article.
If the same code comes back after the fix, contact Whisker support first, especially under warranty. Out of warranty, compare the repair quote with a new robot's price and 3 year cost.
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We read every question. When several owners ask the same thing, the answer goes on this page.
How to read the Litter-Robot 4 light bar
The light bar sits on the front of the base above the drawer. Whisker uses five main colors: blue for ready and drawer status, red for sensor stops and faults, yellow for paused, cycling and pinch events, purple for Sleep Mode, and green or white for calibration and firmware.
Pay attention to the pattern as well as the color. A solid light, a flashing light, two flashing segments and a single light moving back and forth all mean different things. Lights next to the Connect button refer to WiFi.
The four lights owners see most
Flashing blue is the drawer full indicator. Empty the drawer, then press Reset and Cycle. If it flashes with an empty drawer, Whisker says to confirm the unit is plugged in, online and on current firmware.
Solid red means the cat sensor saw a cat. It is not a fault. The unit waits for its cycle delay (7 minutes by default) and then cleans, or cleans right away when you press Reset.
Red and blue alternating means dust or fur is blocking the three curtain sensors in the bezel. Wipe the bezel with a dry cloth and vacuum its inside edge with a brush attachment, passing over the sensor holes at the top.
Solid purple is Sleep Mode, 8 hours a day by default. No Clean cycle runs during sleep, but a visit during sleep triggers one after it wakes. Long press Cycle for 3 seconds to turn it off, or set a schedule in the app under Controls.
Button light patterns
The buttons have their own codes. Whisker lists these as the most common:
- Green or purple round robin: normal operation.
- Green, 1 to 5 solid: cycle delay setting is active. Hold Empty for 3 seconds to save and exit.
- Red and green, 3 solid and 2 flashing: low system voltage. Replace the power supply.
- Blue and yellow, 3 solid and 2 flashing: unbalanced robot or scale feet. Move it to level ground away from carpet, mats, cords and walls.
- Blue flashing Power button: power loss or a defective power supply.
- White Power, Cycle or Reset button: firmware update in progress. Wait.
- Blue with red flashing WiFi light: cannot reach the router. Check the router, then power cycle the robot.
When a light means a part needs replacing
Some codes point to hardware. Red and green alternating means the factory scale calibration is lost and Whisker says the base needs replacing. Green with 2 flashing red that comes back after cleaning and a reset at Home points to a laser board or base. Blue and white alternating that stays after you reseat the motor likely means a defect.
Under the 1 year WhiskerCare warranty, Whisker ships replacement parts at no cost through your account. Out of warranty you buy the part. Whisker support is at 1.877.250.7729.
Litter-Robot 4 profile with 3 year cost
Questions people ask
What does a solid blue light mean on the Litter-Robot 4?
Solid blue is the Ready status. Whisker says the unit should return to a blue ready light after a Clean cycle finishes.
Why is my Litter-Robot 4 flashing blue?
Flashing blue means the drawer full indicator is triggered. Empty the drawer, press Reset, then press Cycle. If the drawer is empty, check power, WiFi and firmware.
What does the red and blue light mean on the Litter-Robot 4?
Red and blue alternating means the curtain sensors are dirty. Wipe and vacuum the bezel sensor area, then run a cycle.
Why is my Litter-Robot 4 light purple?
Solid purple means Sleep Mode is on. Long press the Cycle button for 3 seconds to turn it off, or change the schedule in the Whisker app.
What does a solid yellow light mean?
Solid yellow means the unit is paused. Press Cycle or Reset. If it does not resume, turn the power off and on.