Garmin Varia – rare Firmware Update and Location-Specific Sensor Dropouts ?!?!?!?!?

Garmin Varia RCT715 Review (4)Garmin Varia – Firmware and Location-Specific Sensor Dropouts ?!?!?!?!?

I find that fellow riders tend to talk to me less about Garmin Varia RTL515 in the winter than in the Summer, though I suspect that’s because they are moaning about my lack of mudguards more than my super bright, flashing light. Conversations linked with Varia tend to be short:

  • to someone who hasn’t got one – Get one. They’re good. They stop you from dying.
  • to someone who HAS already got one – do you get those freakin’ annoying sensor dropouts too?

I seem to get sensor dropouts with Varia when using the Edge 540 more than I used to with the Wahoo Bolt 2. Maybe I’m imagining the difference but they happen to some degree regardless of the brand of head unit. This error is the main culprit that seems to annoy me every half an hour or so

Error code 0:9 (Garmin Varia 515)

Garmin Forum Link

Once it happens the error code stays on display. Annoying. With the Edge 540, you can get rid of it by pressing the bottom right-side button. Pressing the button physically moves/rotates the 540 in the mount. Grr. So I hold the Edge 540 with my thumb on the left-hand side to stabilise it and stop it moving. My thumb always, frequently then inadvertently presses the lap button. #Grrr. #Ergonomics. #ShouldHaveBoughtThe840.

So. First up. Why does the sensor drop happen? Then, secondly, why doesn’t the error message just automatically go away a second or so later if the connection can be re-established?

This brings us to a firmware update on Garmin Express that I hadn’t previously spotted. Maybe this will fix it?


It’s good to see new firmware fixing something on the Varia. The last one I remember was an algorithm change at least a year ago. Sometimes these firmware changes also introduce secret new beta features as well as fixing other things. So maybe, just maybe, my long-hoped-for Varia Group Radar is incoming?

Anyway. The following section explains why I think the latest firmware fix will NOT stop my dropout and this is where it gets interesting.

Location-Specific Dropouts

This is one location I’m talking about – Waitrose in Esher. Don’t get excited, I’m not super-posh. I just cycle past it rather than shop in it. Though I did buy a nice Sancerre there during lockdown, but that’s another story.



A couple of Sunday rides ago, a mate said to me as we approached Waitrose, “You won’t believe me but my Varia Radar dropouts here every time I go past it”. I didn’t believe him.

But, sure enough, 20 metres later mine and his dropped connections at pretty much the same time. I scanned around for CIA/Mi5 masts but there weren’t any. I’ve been past a few more times since and the same thing happens every time!! Wow! Each time I looked ever more closely for cellular masts or anything untoward. Nothing. Even the road surface is OK. #Shrug. Although there are some traffic lights 50m or so behind this point.

There MUST be an external signal interference going on here surely?

What do you think?

This is part of many popular cycling routes out of London to the Surrey Hills and thousands of you will have been down this road and know it well. Does anyone else’s Varia work here or fail here?

I’ll update this post IF the new firmware stops the dropout occuring.


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28 thoughts on “Garmin Varia – rare Firmware Update and Location-Specific Sensor Dropouts ?!?!?!?!?

  1. interesting, I get varia (510) dropouts regularly but haven’t noticed a location pattern. I also get dropouts of ther sensors from my edge 530, sometimes everything at once so had put it down as an edge problem, which Garmin support were uninterested in helping with.

  2. I always get a RTL515 dropout in a particular location which is very rural – no traffic lights or owt like that. Most strange.

      1. God, or the Aliens, are amused with our obsession with staying alive (since we’re just going to die anyway) and are messing with us.

  3. I am also getting a particular location drop out. Every single time. It is a rural turn around a church. Nothing visibly special about the place.

  4. On my daily commute I get this error when passing under a motorway bridge. I suspect some speed trap device installed on the overhead motorway. Interestingly enough, it never happens when going westbound, but ALWAYS happens when going eastbound. Next time I’ll have to check somehow if this is related to the side of the road I’m on or if this is related to the direction the radar is facing.

  5. I have several locations where i get a high alert for a fast approaching vehicle, even if im alone. It happens reliable and always.

    I believe this are radar or ultrasonic driven leven indicators because there are some farmers silos. Another place it seems to be a device to expel martens.

    The 0:9 error isn’t appearing on those places with my RTL510, but i see it mostly near high traffic roads if i see it.

  6. Just updated my 515, and feature of this update is that the light now works when plugged into a external battery. Fairly sure that wasn’t a thing before?

  7. I just tried it and it must be specific to the Edge, couldn’t get anything to get going with the 965 unless I was missing a submenu.

  8. It’s power lines/cables, aerial and underground, railway infrastructure etc.
    Electromagnetic field will overload the receiver part and effectively blind the radar, which will go offline until after the interference has cleared.
    Correct behaviour IMHO, it should not stay online when blind due to environment.

    1. makes sense

      in my example, above, there are no obvious cables but i had not thought of underground cables which is possible. would main power cables not be shielded though?? I might try cycling on the wrong side of the road at the same point…that should then be far enough away from anything underground????

      1. Sometimes mid- or even high-voltage power lines are buried below ground, for different reasons. While earth, concrete etc will absorb much of the field they create, there may still be enough to saturate the receiver of the Varia.
        I remember all laptop HDDs being degaussed after having left the computers aboard a small aircraft overnight, parked in a remote corner of Liège airfield, the reason being a high-voltage power line beneath the tarmac… Pilots would also report random compass swings when taxiing past the area

  9. The 0:9 error is a radar saturation error. You’ll usually see it when passed by a car that has blind spot radars, presumably they use the same transceivers.

  10. Any thoughts about future hardware? Currently considering getting a varia radar but it’s 4 years since last update so I’m a bit split on waiting or not?

    1. good question.
      i hadn’t thought about it too much recently
      the 715 showed that garmin NEEDS to create models that in some way justify higher prices/value.
      so i could throw away a comment and predict a new 515 with a better battery and usb-c but i’m not sure garmin will take that route (even though I would like them to)
      i suppose the next big thing would be group radar and then the big innovation to come is in-car sensing of bikes, that’s been on the cards for quite a few years now. i’ll need to revisit where that’s at

  11. Did anyone have any issues with their RTL515 updating to 3.34? I’ve tried Garmin Express and my Edge 530 – it chucks an error out after the ‘backing up’ phase on Garmin Express, but gets to 57% on the Edge device, then the radar light pulses red a few times and it hangs.

  12. Unrelated to updates but on the RTL515, I notice mine will not show on the Varia app as having battery percentage higher than 50% any more no matter how long I charge it. I know the battery is degraded but I wouldn’t think that would be shown in the percentage in the Varia iOS app? Seems like it would still show as fully charged even if it didn’t last as long. Can anyone confirm this is normal behavior?

    1. sometimes electronics have battery %age calibration mechanisms as i dont believe that the charge can be ‘read’ in the normal sense.
      to reset these algorithms you can somtiems charge and fully deplete a couple of times.

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