how do i clean the sensors on my roomba 694? it's bumping into walls more than usual.

Diagnosis

The iRobot Roomba 694 relies on a combination of infrared (IR) cliff sensors and a physical bumper assembly to navigate. When the robot begins "bumping" or colliding with walls more aggressively than usual, it is typically caused by one of two issues: sensor occlusion or mechanical bumper stiction. If the IR sensors on the bottom are coated in a thin film of household dust or pet hair, the robot may perceive a "cliff" where none exists, causing it to abruptly change direction or stutter, which looks like erratic bumping. More commonly, the front bumper—the large plastic semi-circle—has become jammed. The bumper is a floating assembly supported by internal springs. If small debris (like pebbles, crumbs, or pet hair) wedges into the gap between the bumper and the chassis, the bumper stays "depressed." The robot's logic board thinks it is constantly touching a wall, leading to erratic movements, constant reversing, or failure to recognize a wall until it hits it with significant force. You can confirm this by gently pressing the bumper; it should spring back instantly with a tactile "click" sound. If it feels mushy or stays indented, the bumper is jammed.

How to Fix It

Follow these steps to perform a deep clean of the navigation system:

1. Power down the unit completely by pressing the CLEAN button until the lights go off.
2. Flip the Roomba 694 upside down on a soft surface to avoid scratching the top shell.
3. Locate the six cliff sensors (small clear plastic windows) positioned around the perimeter of the bottom. Use a clean, dry microfiber cloth or a cotton swab dipped in 70% isopropyl alcohol to wipe each window. Ensure no streaks or residue remain.
4. Locate the two metal charging contact plates. Use a pencil eraser or a dry cloth to scrub away any oxidation or black carbon buildup.
5. Flip the robot back over. Grasp the front bumper and firmly tap it against a hard surface or gently press it in and out repeatedly across its entire width. This dislodges trapped debris.
6. Remove the front caster wheel by pulling it straight up and out of its socket. Use a can of compressed air to blow out the cavity where the wheel sits, as hair clumps often jam the pivot point, affecting the robot's steering accuracy.
7. Reinsert the caster wheel and power the unit back on to test the navigation.

If That Didn't Work

• Bumper Debris Extraction: If the bumper is still stuck, use a thin needle or a toothpick to carefully probe the gap between the bumper and the robot body. Gently wiggle any visible hair or grit out of the seam. Do not jam the tool deep into the chassis, as you may puncture the internal wiring.
• Hard Reset: Perform a software reboot to clear any "ghost" sensor errors. Press and hold the CLEAN button for 20 seconds. The chime will sound, and the robot will reboot. This often recalibrates the sensor thresholds.
• Check for Interference: Ensure you aren't using high-pile black rugs. The Roomba 694's IR sensors often mistake dark black surfaces for cliffs, causing the robot to "bump" and retreat even if there is no wall present.
• Wheel Inspection: Check the two main drive wheels. Remove the screw on the wheel module and pull the wheel out. If hair is wrapped tightly around the axle, the robot may be pulling to one side, making it appear as though it is crashing into walls when it is actually just steering incorrectly.

Heads Up

• Avoid Liquid Cleaners: Never use glass cleaner, bleach, or soap on the sensors. These leave a chemical film that interferes with the infrared signal, which can lead to the robot falling down stairs.
• Caster Wheel Maintenance: The front caster wheel is a high-wear part. If the wheel feels "wobbly" or doesn't spin freely after cleaning, replace the wheel assembly entirely to prevent erratic steering.
• Sensor Frequency: In high-dust environments or homes with pets, the cliff sensors should be wiped down every two weeks to prevent "Error 4" or "Error 5" messages.
• Bumper Care: Avoid hitting the robot against hard furniture during manual repositioning, as this can bend the internal bumper springs, permanently disabling the collision detection.