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Unreliable GPS with 8 month old 255

Scuffer
over 2 years ago

Hello all,

Just a quick one, I've been with Garmin for about 3 or 4 years now, second watch is a Forerunner 255 which was purchased last August. All firmware is currently up to date.

Recently I've been noticing more and more drop outs in GPS signal mid-run for no obvious reason. As per the below, running the same route 3 times over 3 weeks it is throwing it out at random points in different places. Whilst training for a half marathon this isn't ideal. 

I know the limitations of GPS in built up urban areas/ near body of water, with interference etc. The watch is set to all bands for highest accuracy. 

Effectively, I ran this route a few times and for a few weeks had no issues (but have on other run routes) and then twice in the space of the last week its thrown me off massively in random places. First up is a run where it recorded accurately through including the right start and end point. 

Then last week it threw me off in the middle of a running track and has my end point over half a mile from home. Today, despite  having full lock before hitting start, the first two and a half miles of the run are in random locations when I ran the same route as the first image. 

Again, this is with a watch on highest accuracy settings, full 15 second reset last week after that bad run, with full lock before starting. There are no tall buildings and the start of the tun is in a normal suburban residential area with no tall building or tree coverage to effect the signal. The middle of the run is in a country park and hence I can't understand it throwing me off into the woods from the running track. 

Has anyone got any suggestions or should I be submitting a warranty claim for a bad watch? The watch has suffered so significant falls or damage that should have affected it. 

Any ideas anyone? 

  • 0 over 2 years ago

    I'd try to restart it first, it usually works. ;)

  • 0 over 2 years ago in reply to jpga

    So prior to these runs I had a day or two where no matter what I couldn't get a GPS lock and a restart didn't help. A long button hold restart to clear the cache did. But I shouldn't have to restart the watch every time I want a run to track accurately. 

  • 0 over 2 years ago

    Unless there are someone spoofing the GPS signals in your area, it sounds to me like there is something wrong with your watch.
    My FR255M is very reliable and accurate when it comes to GPS.

  • 0 over 2 years ago

    +1 

    A similar situation. The watch was bought in august, the last month I have some problems with the GPS: long signal fix, frequent loss of signal while running. So, I dont know what really happens (maybe nothing), GPS fine now, but that is my workarounds:

    1. I have updated the watch to the latest beta (15.12)

    2. I found some old CPG file in the RemoteSW folder and deleted it.

    3. These few days I have connected the watch to the computer at least once and it has been synchronized via Garmin Express

  • 0 over 2 years ago in reply to greefon

    What does your watch indicate for the ephemeris status?

    Long press UP -> System -> About ... Ephemeris

    On mine, it is easier to press UP to find System at end of list, UP to find About at end of list, and UP about 5 times to find the ephemeris status page towards end of sequence. Going through the pages via DOWN hits some long delays.

    On mine, I've had it go into "Ephemeris: missing" state a couple times, and I've seen worse GPS performance when it is that way. It takes longer to get a fix and will easily drop out again with slight movements while I am on that initial status screen before starting an activity. The tracking results during the activity will also seem worse.

    To restore the ephemeris file, it seems like I have to have the bluetooth link to GCM on my phone enabled *while* trying to get this satellite lock and start an activity. Doing syncs with GCM outside an activity don't seem to do it.

  • 0 over 2 years ago

    I got my 255 at Christmas and it worked fine until about a month ago. It tracks walking pretty well (not as good as my mobile) but my morning runs for the last few weeks have recorded less than 10km rather than the anticipated 13.26km and recorded crazy fast and slow speeds. I've recorded with my Google Pixel and Fitbit Charge 5 (which is rubbish) at the same time and neither of those have had problems. I was just about to return my 255 as faulty and then today it worked fine for the first time in weeks (only missing 0.15 km compared to the Pixel). Because this has continued for a month all of my data is now junk, should I return it?

    Additionally to this the heart rate monitor is playing up with sections of high readings that are not correct, I double recorded against my super reliable Polar Verity sense and I don't believe the 255 - I know how my heart is behaving and when I'm in the red zone!

    I contacted support via email but no response so far, is this normal?

  • 0 over 2 years ago

    Same here, I bought mine beginning of January. Worked flawlessly until end of March. Now it can take a long time to get a fix and I have frequent signal loss.
    Also current firmware (not beta) and highest GPS accuracy settings.

  • 0 over 2 years ago in reply to 5331943

    Mine is having phases of working well and then failing badly. I am starting to wonder if it is related to which jacket I wear as none of my other devices are having problems - every time I wear my Goretex jacket (which has a foil type lining) with velcro cuffs it seems to fail badly. Is this mad talk? 

  • 0 over 2 years ago in reply to Oly

    Yes, everything is fine for several days, and then suddenly signal lost during run and not restored until the end of the run. And then everything seems to be fine again, for a while. Never had such problems before with 245, 220, 410, 310xt in same locations.

  • 0 over 2 years ago in reply to Oly

    Sounds very plausible to me.

    If it's really some kind of semi-metallic foil to "reflect heat", it might attenuate the very weak radio signals from the satellites too.