Garmin GSC10 problems

Garmin GSC10 cadence sensor

Garmin GSC10 cadence sensor

For an updates to this article with news of the current GSC10 see Garmin GSC10 the Sage Continues.

The otherwise excellent Garmin 705 is let down by the GSC10 speed and cadence sensor. This unit is not properly waterproofed and eventually fails completely. You can revive it once or twice by drying it out but once water ingress causes corrosion or electronic failure the cadence sensor becomes a piece of junk.

It is mystifying to me why Garmin do not correct this problem. The solution is to properly waterproof the unit, surely that cannot be beyond the capabilities of this technologically sophisticated company?

I bought two cadence sensors with the 705 about 18 months ago. They started to fail after a couple of months. I had both replaced twice over the warranty period and now only have one working (which is on a bike used only on a turbo so it never gets wet).

There are quite a few posts on the forums at motionbased including one that describes how to fix the problem although you would need to be fairly skilled electronics engineer to follow the steps, it is way beyond me. A small sample of this solution reads:

It is a 100nF ceramic cap in 0402 (4mm x 2mm) case size. I replaced it with a 0603 size part which will fit ok on the pads. To do this you will need an smt iron and a stereo microscope, and a steady hand.

Note:  The post at Motionbased has been removed by Garmin so it is no longer available, sorry.

What really irritates me is that Garmin are aware of the problem but they do nothing to fix it, and they keep on giving advice to people which just wastes their time. Once these things fail no amount of changing batteries and moving them away from each other will fix them.  Get a new replacement GSC10 and it works immediately with no faffing about, proving the problem is with the unit rather than with incorrect user set-up.

The Garmin website claims the GSC10 has water resistance of IPX7, an IPX7 designation means the unit can withstand accidental immersion in one meter of water for up to 30 minutes. In my experience wash your bike a few times and the GSC10 will stop working. You can dry it out and get it working again once or twice but then it will be dead and cannot be revived again.

See also MACRO 2SXcom speed and cadence sensor

Update: As one of the Macro units I have been using instead of the GCS10 has started to fail I have ordered a new GSC10 to see whether it has been improved in the last couple of years. Will be interesting to see whether it is now better waterproofed, if it lasts at least a cople of years then I will be happy.


5 Responses to “Garmin GSC10 problems”

  1. Evangelos says:

    Do you, by any chance, happen to have kept a copy of that post published in the Garmin forum (and removed by Garmin) you are referring to? I have the same problem with GSC 10 and, since I am into electronics (as a hobbyist), I would like to give it a try before discarding it and getting a new one.
    Thank you.

  2. James Piggot says:

    No sorry I didn’t keep a copy, several people have asked about it. I have searched around but could not find it. I guess Garmin found it embarrasing and took it down. I am currently using two or three GSC10s and they are working Ok in spite of getting wet. The trick seems to be to keep the screw on the arm that measure speed really tight if that is lose then moisture gets in. Good luck with yours!


  3. Evangelos says:

    Hi James,
    Thank you for your response. Mine lasts for about 20 days with a new battery. It’s really frustrating having to replace the battery every now and then. It’s not only a matter of cost, but it’s all the hassle involved.
    Anyway, I consider opening it and trying to find out where the (electrical) leakage is and if I can fix it.
    Best regards,

  4. Mal says:

    Hi James,
    Mine will pick up the crank magnet (red light flashes) but will not pick up the wheel magnet (green light). Cadence is no longer recorded even though the 705 identifies a cadence sensor being present. It appears that the GSC10 unit just presses together. I wonder if a bead of silicon or silicon grease around the seam and around the adjustment screw for the magnet arm might be a useful precautionary measure. Looks like I need a new one judging by the postings.

  5. James Piggot says:

    Hi Mal,

    I was told to make sure the adjustment screw for the magnet arm was tight as you suggest above. Since then the two GSC10s that are on my bikes have been working without problems. You can try to dry it out that sometimes works, just place it on top of something warm such as central heating boiler for 24 hours and see if that gets it working again.

    Good luck,

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