Collision Sensor Problem - Automower Keeps Stopping

Common Easy to Fix Low Cost 10-20 Minutes
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Problem: The error message "Collision sensor problem" or "Collision sensor active" appears frequently. The robot stops seemingly without reason, even though no visible obstacle is present. Particularly common with models 310 and 315.

Problem Description

The error message "Collision sensor problem" or "Collision sensor active" appears frequently, especially with models 310 and 315. The robot stops seemingly without reason, even though no visible obstacle is present. The sensors are in impact mode, preventing the mower from continuing to work. Often contamination under the bumpers is the cause.

Affected Models: Particularly common with 310, 315; also possible with other models (305, 320, 420)

Possible Causes

  1. Grass accumulation under the bumpers (most common cause) – Grass and dirt block the movement of the collision sensors
  2. Housing not correctly seated on chassis – Incorrect assembly after cleaning or repair
  3. Mower stuck under garden furniture – Low garden furniture triggers collision sensor
  4. Dirt between housing and chassis – Prevents free movement of housing
  5. Defective collision sensor (rare) – Electronic defect in the sensor itself

Step-by-Step Solutions

Solution 1: Clean Bumpers

Time Required: 10-15 minutes

  1. Turn off the mower and place it on a level surface
  2. Remove the housing cover (varies by model – usually clips or screws)
  3. Carefully remove the bumpers (usually attached with T20 Torx screws)
  4. Thoroughly remove grass residue and dirt under the bumpers with a brush
  5. Also clean the contact surfaces on the chassis
  6. Reinstall bumpers and screw them hand-tight
  7. Remount the housing
Tools Needed: Torx screwdriver T20, brush, compressed air if available, cloth
Tip: Use compressed air or a compressor to clean hard-to-reach areas under the bumpers. This is particularly effective for small grass seeds.

Solution 2: Mount Housing Correctly

Time Required: 5 minutes

  1. Remove the housing completely
  2. Clean all contact surfaces between housing and chassis
  3. Ensure that no grass residue or dirt is present
  4. Mount the housing correctly (must be able to move freely)
  5. Check: The housing should swing back slightly when pressed at the front
Important: The housing must not sit too tightly! It must be able to move freely so that the collision sensors are triggered in case of impact. Housing that sits too tightly leads to false alarms.

Solution 3: Adapt Environment

Time Required: Variable, 10-30 minutes

  1. Remove objects under which the mower frequently gets stuck
  2. Create islands around low garden furniture with boundary wire (at least 20 cm distance)
  3. Avoid areas with many small obstacles
  4. Ensure garden furniture has at least 15 cm ground clearance
Common Problem Objects:
• Low garden chairs
• Trampoline legs
• Deck chairs and sun loungers
• Garden hoses
• Flower pots with low edges

When Should You Consult a Professional?

If the problem persists after thorough cleaning and correct assembly, a collision sensor may be electronically defective and needs to be replaced. This requires electronics knowledge and special tools. Professional help is also advisable for visible damage to the housing or bumpers.

We offer diagnostics and repair of collision sensors as well as original spare parts for all models.

Preventive Measures

  • Clean bumpers every 2-3 months – Especially in spring and autumn with high pollen count
  • Check housing during every thorough cleaning – Ensure correct fit
  • Keep garden tidy – Free from small obstacles
  • Islands around problem areas – Create exclusion zones preventively
  • Check after strong winds – Branches and leaves can block sensors
Pro Tip: If your mower is particularly susceptible to this problem, you can attach a thin felt strip between housing and chassis. This prevents the smallest particles from entering without impairing the function of the collision sensors.

Need Spare Parts or Professional Help?

Collision sensors, housing parts, and all other components for your Automower can be found in our shop. For persistent problems, we're happy to help with professional diagnostics.

Contact Us Now View Spare Parts
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