Just got a 510 bundle. Did what the worthless manual said to do, the unit works great, heart rate monitor worked fine, but it won't pick up the cadence sensor??? Anyone know why? It suppose to flash green after 2 revolutions, then flash green for 5 seconds . Mine does that but also throws in a few red flashes. Any info?? Or troubles like that??

Green flash is spoke magnet passing the sensor, red flash is cadence magnet passing the sensor. I'd guess the sensor and magnets are setup correctly and you need to pair it on the device under the correct ANT+ profile. I believe that's "Speed/Cadence" for GSC-10 but read this for more details.

The ANT+ Bike Speed/Cadence Sensor: Everything you ever wanted to know | DC Rainmaker

did you pair it?

I remember having a similar problem several years ago when pairing my Garmin 500. If I recall correctly I had to un-pair the HRM, then try to pair the cadence sensor first, then the HRM. If that doesn't work, play with turning bluetooth off and back on, and make sure that all your phones nearby have their bluetooth turned off. Then try again.

I had to reformat my Edge 510 as one of my rides corrupted the Hard Drive and it would randomly turn off in the middle of the ride. Garmin's support was very good. After reformatting, they walked me through repairing it. Instead of using "Speed/Cadence", they had me use "Speed & Cadence" which is a few clicks below and actually off the screen. Once I set that, it was a snap.

You might not have the cadence/speed sensor enabled. Once you enable it then you have to search for the sensors. The sensors are in the bike profile. There is a search function. You should see ANT+Sensors.

^this. My GF's 810 was the same IIRC

i've had issues with getting my display to be readable on night rides lately. used to work fine. * sigh.*

Top of page 7 in your manual.

So I finally figured out how to have both speed and cadence sensors paired and working. I went on 3 rides to test it everything works correctly except when I upload it doesn't show the speed I was riding?? Anymore info on that

Sooo, what did you do to fix it?

Well.. The sensors that I got are the newer ones and didn't match the ones in the photo. After going into bike profiles I saw that both switches were off. So , I enabled them and they are both registering on the head unit as well as on my ride summary page on the upload. On my dashboard it doesn't show speed for some reason still but it is ther on the summary??

Have you set up an account with Garmin Connect and upload a file yet? Take a look at your data on that site. Your phone app may be glitchy.

Speed should be picked up with the GPS. It's mapping so it's obviously enabled. Like someone said, upload to GC or Strava or something and see what the speed it. App is probably the issue.

Thanks for the info!! I got it all working now and the upload is there too.