Garmin 830 momentarily stops and starts the timer while riding?

I'd recommend using the "auto pause" feature instead of just setting it to zero. The sensor found popup is unrelated and usually happens when the ANT+ subsystem on the Garmin has to reset because of some reason.

Anyway, the speed sensor you're (probably) using works by sensing how it moves through the earth's magnetic field. If anything magnetic passes near it, this can cause the sensor to momentarily register additional wheel revolutions or none. For me, it is almost always a bridge that causes a pause. There are several bridges in my area that will trigger this when crossing them, usually around a steel expansion joint.

I had another problem with a magnetized chain causing fluctuations in speed that the only solution was to move the sensor from the rear wheel to the front.

To be honest I don't like the magnetometer-based sensors. My road bike has the old speed/cadence sensor with the spoke magnet. I just recently had to replace the battery for the first time that I can recall, at least 5 years and 100k+ miles, while the other wheel sensor battery I have had to replace several times after less than 5k miles. I think the sensor wakes up when it's on my bike rack, draining the battery faster.

Thank you for the detailed response. I think I may have told you wrong when I said it was set to stop at 0 MPH.

Under the heading of "auto features", I have set the device to "auto pause", but there is a sub menu where one must choose between "off", "When Stopped" or "custom speed". Previously I thought I had chosen "when stopped". I don't remember actually keying in "0mp" under the custom speed field. So, I think I had it set that way all along, but I'm not positive.

My Garmin speed sensor, purchased a year ago, raps around the rear wheel hub.. I assumed it contained an accelerometer which sensed the rotations, rather than working off the magnetic field. But that was a guess on my part.

I will try again, now that I'm sure I have it set the way you suggested.

I will report back.

This is something in the 830, not your sensor.  I have the same issue in the current revisions. I'd suggest you report it to Garmin.   

Used to be perfect, but now it mine randomly does the stop/start.  Normally in the middle of the country, not a magnetic interruption to be found and no repeatability in the same areas.  Works well otherwise, but it is a bit annoying to have the unit beep at me.  

Plus it also has gps running, which of course shows that the device is moving so I think there should be something between the two to figure out if GPS states 20mph, and the sensor stops sending data, it wil gracefully fail and deal with the information drop.

Thx for the feedback.

how does one "report it to garmin’"

I looked and could not find how. Do you know of a link to where I can do this?

support.garmin.com they have contact methods there.

Thx,

I found it at the bottom of one of their pages. I'll report back if I learn anything useful.

Please update us in a week or two.  I've done this and the problem came back, but that was on older revisions.  So it might be better in the 8.x revision. 

I’ve ridden about 4 or 5 times and think I saw it do it once.

so, it seems to be mostly solved