Is it possible to turn light OFF and have radar ONLY

I couldn't get it to work on my 810 but it works reasonably well on my 820.
I suspect the 510 firmware is pretty similar to the 810.

I've just tried with my daughter's 510 and it appears it is not possible to have the radar on and the light off.

it appears it is not possible to have the radar on and the light off.

Thank you.

Not true.
Settings -> Sensor -> Lights -> Network Options -> Light Mode -> Individual
Settings -> Sensor -> Lights -> Radar -> Light Mode -> Off
That's all.

I don't know what type of Edge 510/810 you're looking at, but the ones I have in front of me here don't have those options.
My edge 820, on the other hand does, but as the original question was about an Edge 510, I'll stick by my previous statement. :rolleyes:

Pair Garmin 810/510 with Varia Radar and after that switch off Garmin. That will be turn light off but the blue led will still blinking. Switch on Garmin and it will be paired with the radar but the light will be off. Start your ride :)

Pair Garmin 810/510 with Varia Radar and after that switch off Garmin. That will be turn light off but the blue led will still blinking. Switch on Garmin and it will be paired with the radar but the light will be off. Start your ride :)

I have just tried this a number of times (edge touring plus) and can confirm that it does *not* work. I turn off my Garmin, blue led indeed blinks. I turn on Garmin, it finds radar (lights stay off). But within a few seconds it says "Light network formed" and turns on the lights. :( Hopefully, it might save some time someone else.

Edge 820 finally remembers the Light Mode setting in its latest firmware (6.20)

This is something that Garmin is aware of and we are actively investigating. I do apologize for the inconvenience.

After a year, i believe Garmin has finally fixed this issue. Apparently, the issue is in the Edge bike computers, not the Varia Radar Tail Light (RTL). In the latest firmware (version 6.20) for the Edge 820, here's the description that relates to the RTL:

Added improvements for ANT+ bike lights. Added new Light Beam Activated and network Light Mode settings to ANT+ Bike Lights sensor settings. You can now configure your lights to turn On with a Timer Start by using the new Light Beam Activated setting and there is also a new Trail Light Mode.

There is no description on what the "Timer Start" option does in the Light Beam Activated setting. The other option available for Light Beam Activated setting is "Device Power Up". I don't remember which option the Light Beam Activated setting defaults to, but if you set it to "Timer Start" instead of "Device Power Up", the Edge 820 (and probably the Edge 520 since the latest firmware update included the same description) will remember your Light Mode setting and NOT set it to Overdrive. I tested this by power cycling both the Edge 820 and RLT multiple times. I also tested letting the Edge 820 go to sleep (which then turns off the RTL), waking it up a few minutes later and then manually turning on the RTL. In all cases, the RTL never loses the Light Mode setting. So thank you Garmin for finally fixing this, even though it took a bit longer than i'd initially hoped for.

I have released a data field that let you switch off and on the rear light. I have tested on a TL 301 rear light but I have reports of users using it with the radar version, if you want to give it a try, it's here:
https://apps.garmin.com/it-IT/apps/b20762ef-7027-45d5-84fc-220777b7627f

It works only for devices with a touch screen, so 820 and 1000 series.

Varia forgetful again

Guess what, during my morning commute, i noticed the Varia RTL was in overdrive mode. It seemed to have forgotten the "off" setting again. Now i have no clue what the "Timer Start" setting does.

Guess what, during my morning commute, i noticed the Varia RTL was in overdrive mode. It seemed to have forgotten the "off" setting again. Now i have no clue what the "Timer Start" setting does.

I have figured out what the "Timer Start" setting does. "Timer Start", as the name implies, only turns on the taillight portion of the RTL when you press the start button on your Edge computer. As soon as you save or discard the ride, the taillight turns off. There does not appear to be a way to completely disable the taillight in "Timer Start" mode, even when Light Mode is set to "Off". The choices that affect the RTL when it's in "Timer Start" mode is either "Day Flash" or "Overdrive". Leaving the "Light Mode" in "Off" appears to cause the RTL to run in "Day Flash" mode when the timer on the Edge computer starts.

When the Light Beam Activated mode is set to "Device Power Up", instead of "Timer Start", it is possible to set Light Mode to "Off". However, the bug that causes the Edge 520/820 to forget the "Off" setting still exists. I validated under the following conditions, the Edge 520/820 will forget the "Off" Light Mode setting:

- Varia RTL is manually turned on AFTER the menu on the Edge 520/820 becomes available. If the Varia RTL is turned on BEFORE you power on the Edge 520/820, or if the Varia RTL is turned on within a second or two after you power on the Edge 520/820, the Edge 520/820 does not forget the "Off" setting.

- During your activity, the Edge 520/820 disconnects/reconnects with the Varia RTL.