1690 Works Until I start to Drive - then it cycles off and on

Did your software updating include a firmware update? If so, your nuvi will have to update that first before updating anything else, probably necessitating a reboot or two.

Believe me after many of the users here had this kind of problem with their device regardless of the model number, they had to had replaced the unit. There is no other way you can debug it!
I wonder why no one else other than Garmin customer is having this problem with their devices.

If you have your GPS plugged into a cigarette lighter socket, it's possible that there's a loose electrical connection in that circuit. If so, it would cause the GPS to turn on and off. A good test is to use your GPS on its own battery (not plugged in) and see if it still cycles on and off.

Good call Tuckahoemike! Also, be sure that the 1690 is fully charged before you do this to assure a known good state. You can charge it with an AC will adapter that supplies 1.0A or 1000ma.

I have a 1690 pre Oct build and have had no issues, - mine works great. I am also running all of the most recent updates - be sure to perform a hard reset. Note - you will need to reset you personal preference settings.

Maybe the firmware update, gave it motion sickness. This is why I take my Garmin units out, place them under the back tire and drive over them every couple of years. It doesn't fix anything but It makes me feel better.....

Check for bad connection in the lighter socket. If your car has more than one lighter socket, try the other one. Both of my cars have an auxiliary charger socket in the center console that's on a different circuit from the lighter. Sometimes dirt gets in the socket and makes it work, then stop, then work.

You are assuming WAY too much here.
His problem may have NOTHING to do with the update at all.
It may simply be a bad power connection when in the car.
I'll bet that it will run just fine off the built-in battery.

Often in the past, update problems that do NOT cause a complete lockup can be fixed with a "hard reset" or by doing the update a second time.

No point in crying wolf just yet !!

Garmin contacted me and suggested I do a Master Reset. I did the Master Reset and the system is now working.
BTW - I had the recycle issue if the garmin was plugged into the charger and when it was not plugged into the charger. The recycle would happen as soon as the car would be moving for about 500 - 1000 feet.

Note: A master reset will erase all waypoints or favorites and will restore your unit to the default factory settings. If you would like to back up your favorites you can find instructions below.

Master Reset:
Start with the unit OFF and unplugged from power
Touch and hold the lower right corner of the screen with an index finger or the eraser end of a pencil
Continue touching and holding the lower right hand corner of the screen then power the unit ON
Release the power button when the device powers ON
You will see a new message: Do you really want to erase all user data?
Remove your finger from the touchscreen when this message displays
Touch Yes
The device will automatically reset. Follow the on screen prompts then place your device in an area with a clear view of the sky until it acquires satellites.

Backup Favorites:
In order to back up your Favorites:

Using a USB data cable, plug the device into a computer
Double-click the My Computer icon (Mac users can skip this step)
Right Click the nuvi drive and select explore (Mac users can find this on their desktop)
Double-click the Garmin folder1
Double-click the GPX folder
Copy the current.gpx file
Paste this file to another location on your computer
Rename the file current1.gpx
Once you save a copy of the GPX file on your computer, you have successfully backed up the waypoints within your device.

To restore these Favorites on your device:

Using a USB data cable, plug the device into a computer
Double-click the My Computer icon (Mac users can skip this step)
Right Click the nuvi drive and select explore (Mac users can find this on their desktop)
Double-click the Garmin folder1
Double-click the GPX folder
Copy the current1.gpx file saved to your computer
Paste this file to the GPX folder (You will need to have both the current.gpx and current1.gpx file in this location)
Unplug the device from the computer
At this time the favorites you backed up should be restored on your device.

Congratulations on getting it fixed!

My 1690 starting doing this a few days ago as well. I tested it without the cigarette lighter and it still did it. I will try the reset method discribed above to see it that takes care of it.

It only worked for one day. I had to send the unit back. New one arrived 2 days ago. I am really disappointed. I purchased a Garmin 8 years ago and I never had a problem. I hope this is not a trend.