GPSrChive Discussion Forum

I recently bought a used Garmin GPSMAP 64s. The first thing I did was reset everything from the menus, so unfortunately I do not have a reliable pre-reset baseline.

The receiver otherwise works perfectly: it gets a fast, stable GPS fix, navigation is normal, and GPS/EGNOS satellites show solid, high-contrast signal bars. However, with **GPS + GLONASS enabled**, the GLONASS satellites never seem to become active or contribute to the fix.

The attached photos show the problem clearly: for example, GPS 19 has a normal dark/solid bar, while GLONASS 67 and 73 only have very pale grey bars.

What I have tried:

• Left the unit outside under completely open sky for an entire evening. No change.

• Repeated **Reset All Settings** and **Delete All/User Data** from the menus several times.

• Performed the hardware/master reset using **PAGE + ENTER + POWER**, then confirmed “Erase all user data”.

• Used **Auto Locate**.

• Switched to **Demo Mode**, then back to **Use Satellite System**.

• After some boots, only GPS satellites appear initially. Demo Mode → Use Satellite System → Auto Locate makes the GLONASS columns appear, but they remain pale and unused.

• Downgraded from firmware **6.60 to 5.90**, then further down to **5.50**, and afterwards upgraded to **5.60**. GLONASS behaved exactly the same on every tested version.

• Connected through Garmin Spanner/GpsGate and checked the NMEA output. GLONASS satellite IDs are reported as visible, but they are not used in the position solution.

• Backed up the complete Garmin directory and tested deleting the GNSS data files:

  Code: Select all

  /Garmin/GPS/ARC.BIN
  
  /Garmin/GPS/BEE.BIN
  
  /Garmin/GPS/MT.NVM

• I also deleted the entire `/Garmin/GPS/` directory and rebooted. No improvement.

• There was no `EPO.BIN` or `RemoteSW` directory in the original backup.

Device information:

* Garmin GPSMAP 64s
* Original/current main firmware: 6.60
* Tested firmware versions: 5.50, 5.60, 5.90 and 6.60
* PCB: GPSMAP 64 S V7
* Part number: 006-B1859-00

Has anyone seen this exact behaviour on a GPSMAP 64s? Is there another Garmin-specific GNSS reset/reflash procedure I have missed, or does this point to a receiver hardware fault?

Thank you!

Images

IMG_4253.JPG

IMG_4254.JPG

*** edited to conform with forum posting guidelines ***

Sounds very similar to eTrex Touch Bug 13.

After all the resets and clearing of data, have you reconnected to Garmin WebUpdater and/or Garmin Express to see if any additional updates are pushed through? Perhaps some GPS Constellation files?

GPSMap 64sx, firmware version 3.10

GPS + GLONASS + WAAS/EGNOS

GPSMap 64sx satellite page

gpsmap64sx.jpg

Wojtas81 wrote: Sun Aug 02, 2026 3:07 pm GPSMap 64sx, firmware version 3.10

GPS + GLONASS + WAAS/EGNOS

GPSMap 64sx satellite page

gpsmap64sx.jpg

Thank you!

The GPSMAP 64x series are equipped with a newer GNSS chipset (MT3333).

Yes, and I can switch between GPS + GLONASS or GPS + Galileo.
Both works almost the same, however GLONASS usually provides more satellites.

We dug one of our GPSMAP 64s (v660) units out of mothballs, installed some fresh AA batteries, and placed it in clear view of the sky for more than an hour, and have similar results:

No GLONASS

1195b.bmp

GPSMAP 64s was released in 2014
eTrex 30 was released in 2011

And even very old eTrex 30 has zero issues with GLONASS

eTrex 30 satellite page

eTrex30.bmp

It looks like these GLONASS issues are limited to very specific devices, regardless of their release date.
Something must have been changed in GLONASS satellite system which made some GNSS chips incompatible.

Wojtas81 wrote: Sun Aug 02, 2026 9:04 pm It looks like these GLONASS issues are limited to very specific devices, regardless of their release date.

Both the GPSMAP 64 series (non 'x') and the eTrex Touch 25/35 series use the exact same GNSS chipset (MediaTek MT3332N).

The Oregon 6x0, 7x0 and Rino 75x also use this GNSS chipset. Anyone having any GLONASS reception issues with those yet?

GPSrChive wrote: Mon Aug 03, 2026 3:16 amThe Oregon 6x0, 7x0 and Rino 75x also use this GNSS chipset. Anyone having any GLONASS reception issues with those yet?

Oregon 700, firmware 6.00 - zero issues with GLONASS

Oregon 700 satellite page

oregon700.bmp

eTrex 30, firmware 4.90 - zero issues with GLONASS
Montana 680t, firmware 3.50 - zero issues with GLONASS
GPSMap 66sr, firmware 6.10 - zero issues with GLONASS

Everything above tested in Poland (European Union).

PS.
It may be GNSS chipset firmware issue, not GNSS chipset itself.
GNSS chipset firmware is not the same as the device firmware, however the latter usually includes the former.

Thanks everyone for taking the time to test your devices and share the results. The reproduction on another GPSMAP 64s, together with the working 64sx, Oregon 700, eTrex 30 and other comparisons, was extremely useful and helped narrow this down beyond an individual hardware fault.

I have now opened a support case with Garmin and will forward the findings and photos from this thread to them. Your testing has made the report much stronger. I will post an update here if Garmin provides any useful technical information.