Garmin 800 Displaying Funny Speed

thegodplato
thegodplato Posts: 319
edited March 2013 in Road general
Has anyone else had their Garmin 800 playing up. It is showing cadnece correctly and following a route OK but the mileage is all wrong ( just done 17mile and it says only 3!! ) and the speed is fluctuating between 0 and 6mph. Only just started doing this but I need to get it sorted as 80mile ride on Sunday!
2012 Bianchi Via Nirone Xenon

960 miles in 8 days starting 6th April 2013
www.justgiving.com/teams/cyclemadness

cyclemadness.blogspot.co.uk

Comments

  • Let the battery run flat and re charge it back up
  • thefd
    thefd Posts: 1,021
    Has anyone else had their Garmin 800 playing up. It is showing cadnece correctly and following a route OK but the mileage is all wrong ( just done 17mile and it says only 3!! ) and the speed is fluctuating between 0 and 6mph. Only just started doing this but I need to get it sorted as 80mile ride on Sunday!
    Are you using a speed sensor or just the GPS?
    2017 - Caadx
    2016 - Cervelo R3
    2013 - R872
    2010 - Spesh Tarmac
  • Dorset_Boy
    Dorset_Boy Posts: 6,917
    If using a speed sensor, has the magnet on the wheel been knocked? As a result it may only be intermittently reading each revolution.
  • amaferanga
    amaferanga Posts: 6,789
    Let the battery run flat and re charge it back up

    Why?
    More problems but still living....
  • thegodplato
    thegodplato Posts: 319
    I think it must be the sensor on the wheel. It does seem to be about 1mm away from the black sensor on the frame so wonder if its too close? Will check again when I get home.
    2012 Bianchi Via Nirone Xenon

    960 miles in 8 days starting 6th April 2013
    www.justgiving.com/teams/cyclemadness

    cyclemadness.blogspot.co.uk
  • marylogic
    marylogic Posts: 355
    There are green and red LEDs on the sensor which will let you know if the crank and wheel magnets are correctly placed.
  • schlepcycling
    schlepcycling Posts: 1,614
    Also if you're using the speed sensor check what wheel size it is using because it uses a self calculating function for wheel circumference, whereas it has some way of determining your wheel circumference without you having to tell it. I had this problem when I first used my speed sensor I was riding alongside a friend who was registering 17mph and I was showing just 7mph, when I checked the wheel circumference it was massively out. Once I set it manually it worked fine.
    'Hello to Jason Isaacs'
  • Has anyone else had their Garmin 800 playing up. It is showing cadnece correctly and following a route OK but the mileage is all wrong ( just done 17mile and it says only 3!! ) and the speed is fluctuating between 0 and 6mph. Only just started doing this but I need to get it sorted as 80mile ride on Sunday!

    Could be due to the position of the moon relative to your point on the earth. Certain signals are prone to gravitational distortion when the moon is at certain points which can cause erratic reading. Also there maybe interference from local sources such as motion sensors, radar type speed cameras and electromagnetic fields from high voltage power lines. Loads of stuff can cause this although it usually only happens on budget equipment. See the people you purchased your garmin from.
  • wormo
    wormo Posts: 30
    The other week my garmin was showing I was doing 140 mph. Took off the cadence/speed sensor and back to normal. will re-attach to see if working properly.