Disclosure: LitterBoxLab may earn a commission when you buy through affiliate links. This guide summarizes Whisker documentation; it does not make hands-on testing or ownership claims.
Quick answer: On Litter-Robot 4, flashing blue means the waste drawer is full. Flashing red means the unit has detected a cat or other weight for more than 30 minutes. Flashing yellow means the bonnet has been removed. Look at the whole bar: solid, moving, alternating, or partly flashing lights have different meanings. Check the Whisker app before acting.
| Pattern | Meaning | First action |
|---|---|---|
| Blue flashing | Waste drawer full | Empty the drawer; press Reset, then Cycle. |
| Red flashing | Weight detected for over 30 minutes | Check for a cat/object and level the base; then reset. |
| Yellow flashing | Bonnet removed | Refit the bonnet correctly. |
| Yellow solid | Cycle paused | Press Cycle or Reset. |
| Yellow round-robin | Clean or Empty cycle underway | Wait; keep clear. |
| Yellow ping-pong | Pinch detector active | Stop and follow Whisker support steps. |
| Red + two flashing yellow lights | Globe jammed/overloaded | Allow retraction; unplug before inspecting. |
The LR4 has a multi-segment light bar, so “a yellow light” is not a sufficient diagnosis. A whole bar flashing yellow is a bonnet signal; a single yellow segment travelling around is normally a cycle; and a yellow segment travelling back and forth points to the pinch detector.
Safety first
Keep cats away from the entrance while the globe moves. Unplug the unit before cleaning the waste port, removing a stuck clump, inspecting the base, or touching inside the globe. Never bypass a sensor, force the globe, use an unapproved power supply, or reach into a cycling unit. Stop and contact Whisker for a burning smell, damaged cable, unusual grinding, or a cycle that repeatedly fails.
How to use this LR4 light-code guide
This guide paraphrases Whisker’s current Litter-Robot 4 light-code guide. “Ping-pong” means one segment travelling back and forth; “round-robin” means a segment travelling with the globe. “Two flashing” means two segments flash in an otherwise solid bar.
Firmware, setup state, and optional accessories can change the codes available. LitterHopper and Wi-Fi messages do not apply to every unit. When the app gives a more specific notification, follow it and check for updates. These meanings are for Litter-Robot 4, not Litter-Robot 3.
Blue patterns
| Pattern | Meaning | What to do |
|---|---|---|
| Blue flashing | Waste drawer full | Empty it, Reset, then Cycle. If it returns early, check the liner and use our LR4 cleaning guide. |
| Solid blue + two yellow flashing | Scale has detected weight for over 30 minutes | Remove anything touching the unit. Put it on a hard, level floor—not carpet, a mat, cord, grout line, or against a wall—then Reset. |
| Solid blue + flashing yellow Wi-Fi light | App onboarding mode | Finish setup in the Whisker app if desired. |
| Solid blue + flashing blue Wi-Fi light | Connecting/reconnecting to Wi-Fi | Allow reconnection; check the app and router if it persists. |
| Solid blue + solid white Wi-Fi light | Wi-Fi off | Short-press Connect to reconnect Wi-Fi. |
| Blue/purple alternating | LitterHopper motor issue | Accessory-specific; use Whisker troubleshooting/support. |
| Blue/white alternating | Motor connection issue | Do not force the globe; power off and use Whisker guidance. |
Red patterns
| Pattern | Meaning | What to do |
|---|---|---|
| Red solid | Cat sensor triggered | Normal after entry. Let the wait timer finish; Reset can cancel it when the globe is empty. |
| Red flashing | Cat/weight detected over 30 minutes | Check for a cat, litter pile, or object. Confirm level, clear placement and Reset. See our cat-detection guide. |
| Brief red flash after a button press | Control-panel lockout on | Use Whisker lockout instructions; the buttons are intentionally disabled. |
| Solid red + two white flashing | Globe position not detected | Power off if cycling will not complete; follow Whisker support instructions. |
| Solid red + two yellow flashing | Globe jammed/overloaded; it will try to retract | Allow retraction. Once unplugged, check for accessible debris; do not force the globe. See our LR4 not-cycling guide. |
| Red/green alternating | Factory scale-calibration values lost | Whisker directs owners to replace the base; contact support. |
| Red/blue alternating | Curtain sensors need cleaning | Power off; clean only as Whisker directs. Do not bypass sensors. |
| Red ping-pong | Motion detected in waste drawer | Keep the drawer clear and follow the app/support prompt. |
Yellow, purple, white, and green patterns
| Pattern | Meaning | What to do |
|---|---|---|
| Yellow solid | Cycle paused | Press Cycle or Reset; if needed, power off and on. |
| Yellow flashing | Bonnet removed | Reseat the bonnet; the unit resumes shortly after it is back in place. |
| Yellow ping-pong | Pinch detector active | Do not bypass it. Power off before inspection and use Whisker’s pinch guidance. |
| Yellow round-robin | Clean or Empty cycle running | No fix needed; wait for completion. |
| Purple solid | Sleep Mode active | Long-press Cycle to switch Sleep Mode on or off. |
| Middle white segment flashing | Over-the-air firmware update | Do not unplug or press controls; wait. |
| Solid white + two yellow flashing | Incorrect power supply | Use only LR4-compatible Whisker power; contact support if replacement is needed. |
| Green/white alternating | Anti-pinch fault during power-up | Use Whisker troubleshooting; do not defeat safety detection. |
| Green ping-pong | Curtain sensors auto-calibrating | Normally no action; allow it to finish. |
| Solid green + two red flashing | Sensor auto-calibration failed | Clean as directed by Whisker, then check app/support steps. |
Additional documented LR4 codes
These lower-frequency codes are also in Whisker’s guide. “Partial” means three segments are solid and two are flashing unless noted.
| Pattern | Meaning and first action |
|---|---|
| One to five solid green lights | Cycle-delay setting adjustment. Hold Empty for three seconds to save and exit. |
| Green flashing | Manual cycle completed successfully; no action. |
| Green or purple round-robin | Normal operation; no action. |
| Red/green partial | Low system voltage. Do not use an unsuitable supply; contact Whisker for the correct replacement. |
| Blue/green partial | USB-device issue. Power off, wait five seconds, restart, and disconnect USB. |
| Blue/yellow partial | Robot/scale feet unbalanced. Remove contact or weight, level the unit, then Reset. |
| Yellow/red partial | Laser-sensor or firmware-related issue. Check the app for firmware and follow the current support prompt. |
| Yellow/green or yellow/blue partial | User-initiated 4×4 calibration mode; normally no action. |
| White/blue partial | Power-supply fault. Contact Whisker for the proper supply. |
| Green/purple alternating | Hall-effect-board connection issue. Contact Whisker; do not disassemble the base. |
| Blue/yellow alternating | Manual override. Hold Cycle to manually cycle; power-cycle to exit. |
| Yellow/purple alternating | Scale-calibration/audit mode. Power off, wait five seconds, then power on. |
| Blue/red flashing Wi-Fi light | Router connection failed. Confirm router operation, then power-cycle. |
| Blue/white flashing Wi-Fi light | Wi-Fi-chip fault. Use Whisker support. |
| White Power, Cycle, or Reset during update | Firmware-update status. Let it finish; do not interrupt power. |
Ordered troubleshooting
- Record the complete display. Note color, motion, partial flashes, and app message; a screenshot helps.
- Exclude normal status. Solid red after entry, yellow round-robin, and some green/purple movement are expected states.
- Take the pattern’s first action. Empty the drawer for blue flashing; reseat the bonnet for yellow flashing; remove contact and level the base for scale alerts.
- Power down before inspection. Remove only accessible litter/debris. Do not force parts, bypass detectors, or use a random adapter.
- Reset after reassembly. Run a manual cycle. A repeat at the same point is useful evidence for support.
When to contact Whisker
Use Whisker’s LR4 troubleshooting wizard when a motor, globe-position, scale-calibration, Hall-effect-board, Wi-Fi-chip, or power code remains after the documented first action. Contact support promptly for red/green, blue/white, or green/purple alternating, or when a code returns after cleaning and Reset.
Stop and get help if the globe cannot complete a cycle, the unit is visibly damaged, there is heat/burning smell, or the official procedure calls for a replacement part.
Sources and scope
This article paraphrases Whisker’s LR4 light-code guide. Whisker can change firmware behavior and support steps, so the live app notification and official documentation take precedence if they differ from this summary.
FAQ
What does a flashing blue light mean on Litter-Robot 4?
Whisker identifies flashing blue as a full waste drawer. Empty it, press Reset, then Cycle.
What does a flashing red light mean on Litter-Robot 4?
It means the unit has detected a cat or other weight for more than 30 minutes. Check for a cat, object, or poor placement, then reset when clear.
What does a flashing yellow light mean on Litter-Robot 4?
A whole bar flashing yellow means the bonnet has been removed. This differs from yellow ping-pong, which is a pinch-detector alert.
Is yellow round-robin normal?
Yes. A single yellow segment moving with the globe indicates a Clean or Empty cycle. Let it finish.
Why is my Litter-Robot 4 solid red?
Solid red indicates the cat sensor has been triggered, usually after entry. The robot cycles after its configured wait time unless it detects weight again.
When should I contact Whisker for an LR4 light code?
Contact Whisker when a documented first action does not clear a motor, power, globe-position, calibration, or sensor code, or if the unit is damaged, overheating, or unable to cycle safely.
