I have been having some issues with the GPS on my Garmin that started on a rainy ride. It was particularly problematic on that rainy day. The elevation was blatantly inaccurate. When I would descend, the elevation either stayed the same or even increased! During the first ride when this happened, I couldn't even turn off the Garmin. I had to forcibly turn off the power.

Also, Sometimes, If I am going up a hill, it now frequently goes into AutoPause. It says I'm only going 1 mph, but I know that I'm riding at 4-8 mph. Yet, when I'm walking to the bathroom at the gas station, it says I'm going 4 mph and the Garmin unpauses. Did the rain cause these issues? I thought that Garmins were waterproof. I've never had this issue before and I've done lots of riding in the rain. Would using a speed sensor at least be a bandaid solution?

I don't know if this is connected to the issue with my Garmin, but Strava isn't recording parts of the middle of my activities. For the parts that it isn't recording, it is still adding both to my eclipsed and total time. It is also recording my speed and cadence as 0. In other words, my time was inflated and my speed was deflated. It is still recording my mileage accurately. TrainingPeaks and GarminConnect are recording my activities without any interruptions.

For some context, I was in two crashes. I don't know if my Garmin was impacted in my first crash because I had a concussion. In a more recent crash, I bent the rear bracket, which I then replaced. I still don't see how that would damage the GPS, particularly since my Garmin was working well right up until that rainy ride which was a month later.

If I keep having these issues with this Garmin, what should I do?

The Strava issues are easy to check out: compare your Garmin Connect ride file to your Strava file; if Connect shows the data that is missing from Strava, then you have a Strava problem.

By the same token, is your elevation data in the Garmin Connect and Strava files accurate?

As for the other problems: I suggest your contact Garmin's customer service, which is excellent.

If you are in the USA, then call Garmin Support is one of the things you should do. Even if your Edge 840 is more than 2 years old. If they have too long a wait time, then the IVR will ask if you want to leave your phone number for call back. And they do call you back at the time your phone call would have left the queue and gotten to a agent.

When your Edge 840 got wet, it sounds like the static port must have gotten water in it. That will affect your readings that depend on the barometric sensor. I don't know if that is just a hole or holes in the case or not. I wouldn't think so since these things do have a water resistance rating. So maybe they open into a flexible membrane or something. I've never opened one up.

Your issues of auto-pause is likely just incidental to the other issue. With my old Garmin Edge 500 I used to get auto pauses during my rides. And I even had a speed sensor (gsc-10) The default setting to auto-pause is 0 mph. I set it to auto-pause when <3 mph and never had a issue with it again. Though I can't fathom why that helped. That too may have just be a coincidence and something else I did at the time may have been the real fix. I have not had to do that with my Edge 530.

I've found Garmin (and Wahoo) support to be very good with troubled electronics.
Do give them a try.

Barry

The 840 uses the barometric sensor to determine elevation. A rainy day will have changes in the air pressure which will cause errors in elevation determination. It’s a fact of life with GPS units, plus the actual GPS signal cannot accurately measure elevation.

Also sounds like your AutoPause is set to default of 6mph. Change it to “when stopped”.

Update: I was looking through my files on TrainingPeaks. On the same sections where Strava wasn't recording my metrics, it wasn't appearing in the graph below the map on TrainingPeaks. This leads me to believe that this is a Garmin issue and not a Strava issue. I contacted Garmin this morning. I am sending back the Edge 840 and will be getting an Edge 540. I previously had three Garmins in the 500 series, and never had an issue in or after the rain. I've read that others have had similar issues after riding in the rain with Edge 840s. Thanks for the suggestion to contact Garmin's customer service!

As explained above, EVERY GPS will have issues with elevation when riding in the rain. The barometric sensor cannot accurately read when the air pressure is changing. That's the nature of barometric sensors used on about EVERY GPS cycling computer. It will likely be a problem on a 540 for the same reason. I doubt that switching to a 540 will produce better results, maybe you'll get lucky, but I think the 840 with it's touch screen is a better unit. . Also know that elevation inaccuracies is likely the single most common complaint with GPS cycling computers I read about.