Garmin Nuvi 760 satellites problem

This is the satellite screen from the Nuvi56, it is using 8 satellites to determine it's position, number 9 still has incomplete data and can't be used until it goes fully blue, you need to park the car (not moving) with the Nuvi powered via USB somewhere that has an uninterrupted view of the sky (a mountain area is good). If you can set the time and date manually on the Nuvi this will help, leave the Nuvi in this position for as long as possible. With very old sat-navs this would take sometimes 45 - 60 Minutes, however the Nuvi 760 should not take more than 10 Minutes, if it take longer than this, I'm guessing the unit is faulty, possibly its internal time keeping is way out

If this does not work, you could look at the screen below, viewed by touch + holding the Battery icon for 6 seconds, items of interest are Freq, AGC, Batt Voltage etc.

 

After the Sat-Nav has successfully got a satellite fix, it will store an almanac (knowledge of satellite positions) and also the exact time, this will allow it to get a fix very much quicker next time, however this info. may need the battery to be in good condition to hold a charge because the unit is always running even when turned off. I think the time was correct only when it had a satellite fix and it lost the correct time when it was disconnected from a USB power supply, you could try getting a 'fix' while connected to a USB power supply, then turn the Nuvi off, BUT leave it connected to the USB supply over night, if the Nuvi has the correct time in the morning, it will prove that the problem is the battery and a replacement battery should fix your problem. By the way the USB supply you are using is not powerful enough to power the Nuvi and charge the battery at the same time, you need one that displays 'I Limit 1300mA' not 500mA

 

Yes this is very annoying, some older models of Garmin GPS / Sat-Navs have a pop-up screen that allows connection to a computer or take power only but the newer Nuvis (including my Nuvi56LM) don't have this option. There are three possible causes for this to happen.

1) The power output of the charger will make the Nuvi act differently, if the power output is low, e.g. 500mA the unit will charge only and won't allow navigation because there is not enough power to do both. If you use a higher power charger e.g. 1Amp (1000mA) or higher the Nuvi will allow charging and navigation at the same time

2) If the Nuvi is plugged into a computer, the Nuvi 'sees' both power AND data from the computer and goes into data mode e.g. no navigation

3) The USB cable used to connect the Nuvi has 5 connectors at the Nuvi end and 4 connectors at the other end, Garmin uses pin 4 to tell some units which mode to be in i.e.

USB plug pin1 . . . Nuvi pin 1 +5V 5 volts DC
USB plug pin2 . . . Nuvi pin 2 data
USB plug pin3 . . . Nuvi pin 3 data
no connection . . . Nuvi pin 4 ID connector
USB plug pin4 . . . Nuvi pin 5 GND ground

The Nuvi always uses pins 1 and 5 to get power

If pin 2 and 3 have data on them, the Nuvi goes into computer mode, no navigation possible

If pin 4 is not connected to anything, the Nuvi (sometimes) goes into computer mode, no navigation possible

If pin 4 is connected to pin 5 then navigation is possible (but it may not charge battery unless unit is turned off)

The easiest way to get it working is to use a more powerful charger, but some Nuvis may also need pin 4 connected to pin 5, my Nuvi56 doesn't seem to need anything doing to pin 4

 

Yes, it is sometimes possible to 'Eject' or 'Allow to Remove Safely' a USB device, unfortunately Windows 8.1 checks what kind of device is attached so it will allow an 'Eject' for a USB Flash drive but won't allow 'Eject' for a Nuvi because it recognises that it is an MTP (Media Transfer Protocol) device. I think the internal oscillator on your Nuvi has drifted (either too fast or too slow), when the Nuvi gets a 'fix' it will compare it's clock speed with the satellite's clock and stores a correction value telling the internal clock to speed up for example, this correction value is used next time when it tries to find satellites, which makes it much quicker, however, the unit looses this correction value when all power is lost. The window sill is not a good place to get a 'fix' because 50% or more of the satellites are out of view, if you can power the Nuvi via a USB power pack and take the unit outside it will be quicker

 

The method in your picture is obviously much better for receiving satellite data. If the problem is oscillator frequency offset, I would expect the problem to correct itself automatically once a satellite 'fix' is obtained, however I would expect that almanac data, correct time, frequency offset etc. should be retained while the unit is connected to a good power supply, so that a new 'fix' should be much quicker. It is possible that the battery is still affecting the unit when connected to USB power. From you picture in #4 there are a few concerns:-

1) the Ram Test / Rom Test should be saying 'Ready'
2) The 'Volts' when fully charged (Batt capacity = 100%) and on USB power should be above 4.00

 

Yes, those results look good now, the only confusing thing is that 'I Limit' is unusual, here is what I would expect when unit is powered from the Battery and USB power :-

Item . . . . . . . . . . . . . . On Battery . . . . . . . On USB Power

Batt.Capacity . . . . . . . . 1 - 100% . . . . . . . . . . ------------
Battery . . . . . . . . . . . . . OK Cap . . . . . . . . . . Charging / Charge Done
USB Device . . . . . . . . .No Cable Detected . . . Power Cable
I Limit . . . . . . . . . . . . . .Suspend . . . . . . . . . 500mA / 1300mA

The 'I limit' reading suggests the unit is powered from USB, but the other 3 suggest the unit is powered from battery

 

The I Limit stands for Current Limit, it tells you how much power is being received from the USB connector, 500mA = half an Amp, about how much the unit needs to charge the battery when the unit is switched off, the 1300mA (1.3 Amps) is how much the Nuvi requires when is charging the battery and powering the Sat-Nav at the same time, It is probably not a problem. The special USB cable that is supplied with the Garmin 12V car charger and the home charger connects pins 4 and 5 via a resistor in order to tell the Nuvi it has enough power to charge and power the unit and then the unit displays I limit = 1300mA, with this supply you can also display the secret 'Battery page' like this :-

 

When you turn it back on do you have to use USB power or is it on battery?, It shouldn't lose the time if the battery is still working. The last position may be stored, so it looks like the Nuvi knows where it is, but it doesn't really. You could try charging the Nuvi in the car but sometimes the car won't supply power without turning on the ignition key and it is dangerous to leave the keys and your Nuvi in the car.

 

This may all get fixed when the new battery is fitted, but the unit should not forget the time while the battery is still O.K., It might be worth doing a 'Hard Reset' on the Nuvi, this varies a bit with different models, this will reset the unit to factory default, but I guess in your case that isn't a problem, here is are the steps :-

Ensure unit is off (not standby)

For full off press + hold power for 10 seconds until 'Off' Y / N
appears on screen answer Yes

From off touch + hold lower right hand corner of screen
briefly press power button
continue to hold lower right hand corner for 30 seconds
when Garmin logo disappears release lower right 'touch'
logo re-appears, with copyright information
re-apply touch to lower right hand corner
"erase all user data" message is displayed
Answer Yes