Garmin speed/cadence sensor problem - cannot detect it
I must be doing something wrong. I think the battery is still good (the light flashes) but the speed sensor doesn't send a signal to the head units (Edge 705 and 310XT) I use. Or, the head units cannot pick up the signal. I dunno. I have tried to pick up the signal with and without power meter sensing (power meter present? set to NO) and it just won't work.
Anybody have any clues for me? I believe I have the most recent software for each head unit.
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1) Change the battery anyway
2) Remove the whole thing, take the magnet off the wheel, and pass the magnet over the sensor by hand. They can be touchy about the distance between the magnet and sensor
3) Press the reset button
Sorry - thats probably not much help.
I believe you use TR, so is that picking up your data feed? If not, then probably not a 705/310XT issue. Typically the biggest issue is the magnet placement. I would hook up TR so you can see the screen and then just free spin the wheel while moving the magnet around to see if it will connect. Next up would be battery, but if lights are blinking, then they are probably good.
TR was not picking up any speed information.
Just saw this thread, but that was going to be my first guess. If you have a Garmin GSC-10 (combined speed/cad sensor) that used to be working, but no longer is, it is almost always one of two things. First the battery, if you check that and you still can't pair, it's most likely the reed switch in the sensor arm that is broken.
A reed switch is a simple and cheap electrical switch that responds to magnets, and it is what actually responds to the speed or cadence magnet as it passes by, closing a circuit and sending a signal to the the rest of the sensor. Why I mention this is because this switch is by far the cheapest and simplest part of the speed sensor, the major cost and complexity of the unit is in the wireless transmission of that signal via ANT+, not in it's original detection.
Unfortunately, the reed switch, as it is mounted in the movable sensor arm on the GSC10, is also by far the most frail component of the system and routinely breaks if the sensor arm is hit by a spoke or the crank arm. While you can replace the switch alone, it requires cracking the plastic casing of the sensor arm and mangling the whole thing. I've replaced the sensor on one to use it for an indoor bike over the winter, but my hack repair job wasn't good enough to inspire confidence for an outdoor-worthy repair.
Telling you all of this is not really necessary, however the takeaway (if there is one), is that I consider the GSC10 design flawed and would not purchase another one personally. It's certainly not the end of the world that you already have, but I'd go with a design that does not have the reed switch so vulnerably positioned rather than spending 50 bucks a pop to pay for Garmin's mistake.
What would you recommend instead?
If you need both speed and cadence, I'd recommend something like the Wahoo speed/cadence sensor (http://www.wahoofitness.com/Products/Wahoo-Fitness-Wahoo-Cycling-SpeedCadence-Sensor.asp ) over the Garmin since the cadence sensor is secured to the chain stay in a fixed position. My overriding problem with the GSC10 is that the sensor arm seems to invariably end up pushed too far out at one point or another and get whacked by your spoke or crank arm, breaking the reed switch.
Alternatively, if you have a Trek that supports it, I'd go with a Duotrap since I'm all for slick integration.
Note that Bontrager makes a 'no zip-tie' speed/cad sensor that is very similar in design to the GSC10, but looks a little slicker and is held in place entirely by rubber bands instead of zip ties. However, take a look at DCR's review and see what happened to his: (http://www.dcrainmaker.com/2012/02/bontrager-ant-bike-speedcadence-sensor.html ). Guess what, his sensor arm got bumped into his spokes and shredded the arm off. Hence why I don't buy that style anymore.
But personally, the speed/cad sensor I use is... none. I have a Quarq which provides cadence, and my GPS takes care of my speed. If you have a PT that will of course do speed and estimated cadence that is usually close enough. Granted, for indoors, or if you don't have GPS, you may still want a dedicated speed or cadence sensor, in which case go with one like the Wahoo, a dedicated speed or cadence sensor with no extra 'arm' at all, or just be extra careful with your GSC10 or similar.
When using the GSC 10 (as I do), one thing to consider when you set it up is whether to have the "arm" swung upwards or downwards (the latter meaning right near the chain stay, and the former meaning sticking up into the air). Depending on the exact geometry of your bike, you may be able to use it in that "down" position and have it be a little less vulnerable. I guess I've been lucky...never had any trouble for as long as I've had mine.
As for the GSC-10, of course it's not certain doom if you have one. I used one fine for almost 2 years and don't think I ever had a problem with it. Then I killed two within the span of a few months and that sort of soured my opinion on it.
I will admit though, I took some small enjoyment in seeing DCR shred his too. Glad I wasn't the only one, although I've never damaged one quite that bad.