Thread: Garmin Montana 600 «------Big probleme

So it's now obvious that the device also boots normally, i..e. it isn't stuck on the calibration screen and only enters calibration mode when you intentionally hold down the power button.

So let's be totally clear about this:

• The device is in preboot mode immediately before it shows the calibration screen and it will show in Device Manager but NOT in Windows File Explorer if connected to PC in preboot;
• Pre-boot mode is required to flash a firmware RGN with Updater.exe;
• You can only downgrade firmware one of two ways, using either Updater.exe in preboot or using SD card text commands. Using Updater.exe with an RGN correctly is inherently safer but flashing BINs using SD card method is simpler for many users (provided the older montana firmware contains the required "xrgn" command);
• Downgrading to a much lower firmware version should, but not always, force the device to hard-reset and show a screen which can be used to return to factory setting HOWEVER there is no guarantee that the screen will work after that reset, particularly if the problems encountered are not due to software issues (because it's entirely possible the satellite fix not working and then non-responsive screen are not software related.

In explanation of the last point, you may find that the PCB or flash chip is at the root of your problems. A partial failure of the chip could result in such erratic behavior which will worsen and eventually complete failure will likely result. Corrosion on the board might also give similar problems and might have occurred because of moisture entering due to the power button rubber-boot deterioration.

If you want to try downgrading (at your entire risk of course), take the lower version GCD fw and use RGN_Tool to convert it to an RGN file, name it only as 127501000xxx.rgn (where xxx is the 3 digit firmware version) e.g. 127501000590.rgn for V5.90. Flash with Updater.exe in preboot.

If you aren't comfortable making the RGN file let me know and i'll make it for you, or i can make you an SD flash kit if you want. Be aware that if there's a flash chip fault that forcefully flashing firmware may stress it to the point it fails completely. I can take no responsibility for an adverse outcome in any case of course.