Litter-Robot 3 not cycling: causes and fixes

A Litter-Robot 3 that is not cycling is usually waiting on its cycle delay, in Sleep Mode, not sensing the cat, or stopped by a full drawer. Here are the causes and fixes from Whisker's support site, matched to the light you see on the control panel.

Researched by Riley Hart · updated Oct 27, 2026 · How we research

Short answer

Check the control panel light first. Solid blue with no cycle usually means the cycle delay is still counting (7 minutes by default), blue and yellow together mean Sleep Mode, flashing blue means the drawer is full, and slow flashing yellow means a cycle was interrupted. If no light turns red when your cat goes in, the cat sensor is not seeing it, often because of a mat, carpet, a wall or too much litter. Fix the cause, then press Reset from the Home position.

Find your code

What you see	Likely cause	Fix
Solid blue, no cycle yet after a visit	Cycle delay is running (3, 7 or 15 minutes, 7 by default)	Wait for the delay. To change it, hold Empty for about 5 seconds, press Reset to step through, then hold Empty to save.
Solid blue and yellow together	8 hour Sleep Mode is on	Hold Cycle until the yellow light turns off.
No red light when the cat goes in	Cat sensor not triggered: cat under 5 lb, carpet or mat, cords under the base, or less than 1 inch from a wall	Move it to a firm, level floor with 1 inch of clearance, clear cords, press Reset and power cycle.
Slow flashing yellow	Cycle interrupted by the cat sensor or a removed bonnet	Press Reset to resume, then check placement, litter weight and that the bonnet is seated.
Flashing red	Cat sensor triggered for 2 minutes or more	Remove extra litter, keep it under 10 lb and at or below the fill line, fix placement, then press Reset.
Flashing blue	Drawer full. The unit cycles 2 more times, then stops	Empty the drawer, tuck the liner into all four tabs, press Reset at Home, then Cycle.
Solid yellow, globe not moving	Paused, globe not seated, loose motor gear or failed motor	Press Cycle. If it stays yellow, reseat the globe and turn the black key, then check the motor gear set screw.
Fast flashing yellow	Pinch detector stopped the cycle	Unplug, remove the globe, vacuum the dump port, press the pinch bar and clean the two pinch contacts.
Yellow and red, or blue and red, flashing	Motor over torque: the globe is jammed or overloaded	Bring litter at least 0.5 inch below the fill line, clear the globe and waste port, check glider buttons and seal strips.
All three lights flashing	Globe position fault: cannot find Home or Dump	Check the power supply and outlet, clean the base and seal strips, and check the position sensor and globe magnets.
No lights at all	No power	Test the outlet, confirm the supply reads 15V DC 1000mA (1A), check the cord and open a collapsed power jack pin gently.

From Whisker's Litter-Robot 3 buttons and lights, cycle delay, Sleep Mode, cat not detected, yellow flashing, drawer full, pinch sensor, motor over torque, globe position and no power support articles, checked October 27, 2026. We do not test hands on; every fix comes from Whisker's support pages.

Still broken?Repair or replace

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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Step by step checks, in order

Whisker's Litter-Robot 3 lights tell you most of what you need. Solid red means a cat was sensed and the delay has started. Flashing red means the cat sensor stayed triggered for 2 minutes or more. Work through the free checks first.

Wait out the cycle delay. The default is 7 minutes, and you can set 3, 7 or 15 minutes on the unit or under Controls, Cycle Delay in the Whisker app.
If both blue and yellow are lit, Sleep Mode is on. It turns the cat sensor off for 8 hours, repeating every 24 hours. Hold Cycle until the yellow light goes out.
If the drawer light flashes blue, empty the drawer, press Reset Gauge in the app if you use it, and tuck the liner into all four tabs so it cannot block the DFI sensors.
Press Power to turn the unit off at Home, then press it again. The unit runs a Clean cycle and takes a new weight reading.
Test the cat sensor: press the top of the entryway, not the bonnet, down and away. It should spring back slightly and the light should turn red.

When the cat sensor does not see the cat

The Litter-Robot 3 cat sensor is a weight sensor in the base. Whisker says not to use automatic mode with kittens under 5 lb (2.2 kg). A cat that only steps on the front step may not trigger it either.

Placement matters. Put the unit on a firm, level floor, not on carpet or a litter mat, with no power cords under the base and at least 1 inch from walls and furniture. On tile or wood it can slide into a wall over time. Keep litter at or below the fill line and under 10 lb (4.5 kg), and for heavy brands about 0.5 inch below the line. Whisker warns against lightweight litter. Press Reset after any change in weight, and deep clean or soak the globe every 3 months, more often with several cats, since hidden clumps add weight. If it still misses the cat, remove the bonnet, globe and drawer and check that the cat sensor module is plugged into the wiring harness at the back of the base.

Mechanical stops: motor gear, pinch sensor and jams

Solid yellow with no globe movement can be a pause, a globe out of its tracks or a loose motor gear. With the globe out and the bonnet back on, find the black gear behind the control panel cover on the right side of the base. If it wiggles on the shaft, tighten the set screw using Whisker's loose gear guide. If you hear the motor but the gear does not turn, tighten the screw. If you hear nothing, the motor needs replacing.

Fast flashing yellow is the anti pinch safety feature. Vacuum litter around the dump port, press the pinch bar on the left of the waste port several times, and clean the two metal pinch contacts with a dry cloth or cotton swab until they are shiny and touching. Yellow and red or blue and red flashing means the motor is over torque. Reduce the litter, clear clumps or toys from the waste port, check that all four white glider buttons are in place and that the four seal strips are stuck down, and wipe the top of the base with a damp cloth. Whisker notes plant based litter holds more moisture and can corrode internal parts.

Parts, warranty and when a new robot makes sense

Whisker names the parts for each fault. A cat sensor that still fails needs a Litter-Robot 3 Base. A pinch or drawer full fault needs the Pinch Contact and DFI Kit or a base. A motor fault needs the motor assembly, and a power fault needs a new Litter-Robot 3 Power Supply rated 15V DC 1A, which Whisker suggests trying before a base. Glider buttons and seal strips are sold separately. For all three lights flashing on units built before February 2018, Whisker recommends removing the internal shield and offers a free Key and Plug Kit with code KEYANDPLUGKIT.

Under the WhiskerCare warranty, log in at litter-robot.com, open My Robots and request the part; it ships free with instructions. Out of warranty you buy it. Whisker support is at 1.877.250.7729, Monday to Friday 9 AM to 9 PM EST and weekends 9 AM to 5 PM EST. If your out of warranty unit needs a base plus a motor or power supply, compare that parts bill with the price of a new Litter-Robot 4 or 5 before you repair it.

Newer Litter-Robot models in our rankings

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Questions people ask

Why won't my Litter-Robot 3 cycle after my cat uses it?

It waits for its cycle delay first, 7 minutes by default. If blue and yellow are both lit, Sleep Mode is on. If the light never turns red, the cat sensor is not seeing the cat.

How do I reset the Litter-Robot 3 cat sensor?

From the Home position, press Reset. Whisker says to do this after emptying the drawer, adding or removing litter, cleaning or moving the unit.

What is the minimum cat weight for the Litter-Robot 3?

Whisker says not to use automatic mode with kittens under 5 lb (2.2 kg).

What does slow flashing yellow mean on a Litter-Robot 3?

A cycle was interrupted, by the cat sensor or a removed bonnet. Press Reset to resume. After a cat leaves, it resumes 15 seconds later.

Why is my Litter-Robot 3 stuck on solid yellow?

It started a Clean cycle but the globe is not turning. Press Cycle, reseat the globe and turn the black key, then check the motor gear set screw.