My garmin gps will not charge and it will not stay on.

Unfortunately, the problem is with the charging port on the unit, which is from wear and tear. If the charging cable will not stay connected due to damage on the port, the best bet is to replace the entire GPS. You'll notice the port damage when the charging cable is fully seated and it still "wiggles" around. While Garmin's technical support may, and I mean may very loosely, offer a repair option at a fee it may be best to replace the unit with one of the newer models that include lifetime maps and the latest firmware. If the damage is to the cable, then it's a much cheaper option to purchase a replacement.

The Nuvi 780 is an older GPS. Most likely, the battery needs to be replaced due to age. Many lithium-Ion batteries are only good for 2 years. More information can be found here:

http://www.sharc.net/gps_battery_repair.htm

Please have the battery replaced by a professional. We have repaired many units from failed battery replacements by customers. Often other things get broken in the process, sometimes beyond repair.

I think you need to update your Garmin GPS. if you need any type of help about updating ask here. There is a website which shows how to update garmin gps shown below.
Garmin Map Updates

http://www.newpower99.com/ProductDetails.asp?ProductCode=GARMIN+NUVI+760&Show=ExtInfo

If you're "recharging" via the car charger - you might want to try charging via USB jack on your computer - or AC adapter (if your GPS shipped with one) for 5 or more hours.

Many Garmin units develop this condition when used strictly in the car / cigar outlet power source. While connected to your computer, you should go to Garmin's website and download, install & run the "webupdater" software. When complete, your Garmin GPS will have the latest firmware and patches to the software (not maps!).

After charging via USB or AC adapter, your GPS should stay on. If your GPS turns on via a slide switch on the top, Slide the switch from OFF and hold in the ON position for 10 seconds before letting go of the switch. This should force a "boot" on the GPS.

If you're unable to get the device to power up, contact Garmin Support to determine if your device is affected by a a recent battery recall or if there are other suggestions they have to solve the problem.

I hope this helps!

Disconnect the nuvi from the car charger and connect it to your computer's USB port with the supplied cable (or any USB cable you have that fits it), and leave connected overnight (8 + hours).

You should be able to get the GPS to start up as expected after charging via USB port. if this happens again, simply repeat.

Good luck!

If you are plugging it into your computer, or charging it through the USB port, the Garmin NUVI will go into "DATA MODE". You must use the car cradle to charge it and stay in navagation mode.

Connect the Garmin using the USB cable to your computer. Turn on your computer and let it boot up. Now turn on the Garmin. Does it stay on? If the answer is yes then the battery is dead. If the answer is no then you have something internally wrong with the Garmin. If the unit is still under warranty then get a RMA and send it back to Garmin.

How did you charge the unit? If you have not done so, try charging in on the computer for a few hours. Sometimes this can help.

Dead Battery. Garmin will replace battery for a charge if the unit is out of warranty.