Old Nuvi 750 - acquiring satellite

A "factory" reset removes all user data. It should not have removed maps.

I would make sure you have the device (fully charged) with a clear shot (outdoors if possible) to satellites which tend to be in the southern sky. Since the device likely has been moved a considerable distance since it was last used, it might take 10 to 15 minutes to acquire the satellites. See https://support.garmin.com/en-US/?faq=YyCZrQHhuf6PO6qTKdvvr9 for some more help.

The following are the factory reset instructions.

Factory Reset Instructions
1. Start with the unit OFF and unplugged from power

2. Touch and hold the lower right corner of the screen with an index finger or the eraser end of a pencil

3. Continue touching and holding the lower right hand corner of the screen then power the unit ON

4. Release the power button when the device powers ON

5. 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

6. Touch Yes

Do I need a one time purchase to be able to use satellite signals by Garmin?

The one-time purchase or lifetime purchase applies to the purchase of a map, not the use of satellites.

Have you tried what I called a "Factory Reset"?

Yes, I've tried that already. Same thing.

One more thing I did was, I tried installing maps opensea maps manually and with storage limitations I moved the original map file on my desktop and added the opensea one. Then I couldn't get it fixed so I restored the original map files from my desktop back to the device. The two files that were moved are disc files. gmapbmap and gmapprom.

For now, just try to get the device working with "native" Garmin software (as opposed to opensea).

Do you have Garmin Express on your PC and if so when you connect to that what type of behavior do you get? It can be downloaded from https://www.garmin.com/en-US/software/express/windows/ if needed.

If you plug it into a computer using a mini USB cable, will it go into mass storage mode where you can access the file system? If so, see if Garmin Express will offer any updates. Over the years, these old nuvi's did have software updates as well as some GPS chipset updates which could affect its ability to access satellites.

If this unit hasn't been used for a long time, it could take quite a while for it to get a satellite lock the first time ... possibly a half hour or more. If you observe the satellite acquisition screen, you should see the results of its searching showing different numbered satellites pop in and out on the signal chart. On these old 7xx nuvi models, you get to the satellite acquisition screen by pressing and holding the upper left corner of the main screen (where it shows the bars).

Any map update that the device is eligible for might also require an SD card. You should be able to find a slot for the card on the device. Maps have gotten quite large so additional memory beyond what is built in is needed.

The maximum size of the card is 32 GB. It can be something you might have from an old phone, etc. but you will need to format it and hence lose any data on it.

First thing is to check it can still get a satellite lock. As already said this could take a while, so place it outside with a clear view of the sky and relax ... give it a good hour. If it has a fix then move on to maps as maps are no good if the device can't locate the satellites

If I recall, these units that were preinstalled in a vehicle had some proprietary firmware modifications so they would show a special logo (like the vehicle branding) on the startup screen. I am not sure how (or if) Garmin Express handles these proprietary firmware mods.

You can pick up a used but working nuvi 750 on ebay pretty cheap, so that may be another option for you. Again though, I am not sure what the impact is when replacing a vehicle factory installed nuvi 750 with a standard "off the shelf" 750. The nuvi 7xx series is one that used a powered cradle, so I assume the vehicle factory installed models provided power through the cradle pins on the bottom of the device rather than through a USB connection. Hopefully that connection would be compatible with an "off the shelf" standard nuvi 750.

FWIW, my wife's old 2012 Suzuki Grand Vitara had a Garmin GPS in a tray on the dash. I don't remember the exact model but it was in the Nuvi 26XX series. It had proprietary software that was only updatable by a dealer.

I tried buying the same Nuvi model from Garmin but it wouldn't work. It fit the mounting cradle but lacked the 6 contacts on the bottom of the unit.

I tried swapping files from the Garmin unit I bought into the Suzuki but I could never get it to load map files. We ended up trading the vehicle before I could resolve the problem.

In any case, there is a Nuvi 760 in working condition right now on eBay for $6 plus $7 shipping. It would be worth the price just to experiment with.

https://www.ebay.com/itm/175281923176?chn=ps&_trkparms=ispr%...

There is also a used 750 for $8 plus $15 shipping

https://www.ebay.com/itm/324170282615?chn=ps&norover=1&mkevt...

One of the things I liked about the old 7XX series GPSr's is they had an FM transmitter and MP3 player which few newer units have.

I think the only difference between the nuvi 760 and the 750 is that the 760 came with the GTM-25 power plug / traffic adapter, and the 750 just had a plain (non-traffic) power plug. The basic devices were identical. If that is incorrect, I am sure someone will correct me.

Edit: just remembered ... the 760 also had bluetooth and the 750 didn't so the basic devices weren't identical.

Garmin has built in map protection so generally speaking, swapping maps around various devices isn't going to work.

It actually is possible to extract that boot image and replace the boot image in the stock firmware with it. Replacing the boot image is how I was able to add to my 1300LM the routing capability found in devices like the 1450. That custom boot image by the car manufacturer is how that company provided features not found on a "normal" 750.