my roomba 694 just beeps once and won't start cleaning, the clean button is lit up but it just sits there.

Diagnosis

The single beep followed by a "freeze" state on the iRobot Roomba 694 typically indicates a critical sensor failure during the pre-flight check. While the Clean button is illuminated, the robot is failing to transition from "Standby" to "Active" because it cannot verify a closed-loop system. This is most commonly caused by a failure in the bin detection circuit or a blockage in the airflow path that triggers a vacuum motor overload protection. Specifically, the Roomba 694 uses a physical switch and an optical sensor to ensure the dust bin is fully seated. If the bin is slightly skewed or the yellow release tab isn't locked, the robot will beep once to signal an error and refuse to engage the drive motors. Similarly, if the filter is completely saturated with fine dust, the vacuum motor experiences high resistance (backpressure), causing the onboard controller to abort the start sequence to prevent the motor from burning out. You can confirm this by attempting to start the robot; if it beeps once and the "Clean" light stays solid without any wheel movement, it is a sensor-blockage issue.

How to Fix It

To resolve the start-loop and clear the sensor error, follow these precise steps:

1. Power down the unit by pressing the Clean button once to turn off the lights, then lift the robot off the Home Base.
2. Locate the yellow release tab on the side of the dust bin. Press it firmly and slide the bin completely out of the chassis.
3. Inspect the bin's contact points. Ensure there are no clumps of hair or debris lodged in the cavity where the bin slides in, as this prevents the bin from seating flush against the internal sensor.
4. Remove the pleated filter from the bin. Tap it sharply against a hard surface or use a handheld vacuum to clear the pores of the filter. If the filter is grey or black, replace it with a new Part # 694-Filter.
5. Slide the bin back into the robot. You must hear and feel a distinct "click" from the yellow tab. Push firmly on the center of the bin to ensure it is fully seated.
6. Perform a hard reboot: Press and hold the Clean button for exactly 10 seconds. The lights will flash or cycle.
7. Place the robot back on the Home Base, wait for the charging light to stabilize, and press Clean again.

If That Didn't Work

• Check the Bumper Sensors: A stuck bumper can mimic a start-failure. Press the front bumper in and out rapidly 10 to 15 times. If the bumper feels "mushy" or doesn't spring back instantly, a small piece of debris is likely lodged behind the plastic housing, preventing the robot from confirming it is clear to move.
• Clean the Cliff Sensors: Use a clean, dry microfiber cloth to wipe the five silver-colored cliff sensor windows on the underside of the robot. If these are coated in a film of dust, the robot may believe it is perched on a ledge and will beep once and refuse to move for safety reasons.
• Inspect the Main Brush Module: Remove the two green locking tabs and lift out the main brush assembly. Remove the end caps and clear any tightly wound hair or string. If the brush is too jammed to rotate, the motor will trip a circuit breaker immediately upon pressing Clean, resulting in a single beep and a shutdown.
• Battery Reset: If the software is hung, remove the battery. Unscrew the bottom cover, disconnect the battery lead, wait 30 seconds, and reconnect it. This clears the volatile memory and forces a fresh hardware handshake.

Heads Up

• Filter Maintenance: Replace your filters every 2 months. Using a clogged filter doesn't just reduce suction; it puts immense strain on the vacuum motor, which can lead to permanent board failure.
• Bin Seating: Never force the bin in if it feels resisted. Check for "dust bunnies" inside the robot's internal chute first; forcing the bin can bend the plastic sensor pins.
• Avoid Wet Debris: Never use the Roomba 694 to pick up damp debris. Moisture in the filter or bin will trigger the airflow sensor and cause the robot to freeze and beep.
• Charging Contacts: Periodically wipe the two silver charging contacts on the bottom of the robot and the base with a cotton swab dipped in rubbing alcohol to ensure the robot has full power before attempting a clean cycle.