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"Rear bumper disc" on RL1000

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  • gautelund
    I ve got the Rear bumper disc error on an RL1000. I have looked over what has been posted about this in the past. I am quite sure neither solder nor wires
    Message 1 of 1 , Aug 26, 2012
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      I've got the "Rear bumper disc" error on an RL1000. I have looked over
      what has been posted about this in the past. I am quite sure neither
      solder nor wires are broken.

      Here's what I have figured out about the bumpers per se: (skip (or
      correct) if you know Robomow's internals intimately)
      There is a 39 kΩ terminating resistor on the right side of the
      bumper, between the contact strip and the bumber mesh on the inside of
      the bumper rubber. (I even peeled of the shrink tube on the resistor and
      confirmed it was labeled 39 kΩ before I also found that info

      There is a 7-pin connector plugged into the main board, with 6 wires,
      i.e. 3 pairs. Each pair is a black and a white wire. One pair goes to
      the left of the front bumper, one pair to the right of the front bumper,
      and one pair to the rear bumper.

      No broken wire(?)
      If I measure in said "bumper main board connector" the resistance
      between the to pins who correspond to the rear bumper wire, I get 39
      kΩ. If I press the bumper, resistance drops to 1-3 Ω. This
      seems quite sane. If I insert the connector, I can repeat the
      measurements between the two corresponding soldering pins on the back of
      the main board. But if I insert the mower battery and it boots, it
      displays "Rear bumper disc" after a few seconds.

      If I disconnect "bumper main board connector" completely, the error
      changes to "Bumper disc", obviously meaning "all bumper disc". So the
      main board and firmware do seemingly read the front bumper status

      Possible reason, somehow?
      When I opened the mower to look at the problem, the main board was out
      of position. Probably from the last time I had it open, this spring,
      relyplacing a motor and more. The erroneous position had made this
      bumper connector and one other connector snap out, from tension in their
      respective wires. I was delighted to see this, plugged them in, and was
      expecting everything to be OK. But alas, symptoms are as described
      above. I though about broken wire or even broken soldering pin on main
      board, but as stated above: Ω measurements indicate that all of
      that is OK.

      I tried cleaning the surrounding area of the main board with circuit
      board cleaner.

      I fear a fault on the main board. Or could the error somehow have gotten
      "stuck"? Is there a reset procedure I can try? Any other ideas?


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