How to fix the "one hour off" problem in a Garmin nuvi
I had this happen on two Garmin nuvi 30 models I acquired, but it can also happen on a number of other nuvis as well.
This is, as far as I know, the only documentation that exists for this. I had to figure out how to fix this stuff myself.
Here's what happened:
I acquire a Garmin nuvi 30 from eBay. It arrives, and the battery is absolutely stone dead. This did not surprise me since most people who sell used GPSes haven't turned them on in years.
Battery is charged, still works. Good. I then update the firmware. That also goes through without a problem.
Then I notice the clock is off by one hour. Hm. Weird. It shouldn't do that since the time is acquired from the GPS signal itself. I am in Texas in the Central Time Zone, but that shouldn't matter?
I plug in the GPS to my PC, go to the nuvi's hidden .System folder, make a copy of the gmaptz.img file (that's the time zone map) as a backup, then delete it off the nuvi. After that, I update the nuvi again to download the latest time zone map. Nope, still didn't work. The clock is still off by an hour.
I set the GPS to simulation mode, then purposely did the "Set Location" thing to make the nuvi think it was in Sacramento California to see if the off-by-one-hour would carry. It did. Now I know that the unit isn't recognizing Daylight Savings Time at all.
I did some Googling. Only one discussion is on this topic, but with no info on how to fix it since none was ever found.
There was however one part of the discussion that said if it wasn't the time zone map, it might be some other file that went screwy and was causing the problem. This was all I had to go on.
In my possession I had a nuvi 50LM which had no issues with the clock showing the correct time. I just outright guessed the nuvi 30 had the same file system as the 50, and that if any files were corrupt or not working right, I could just copy over the right files from the 50 to the 30, all would be well and the clock would show the correct time.
I was right. That's exactly what it was.
In the hidden .System folder is a subfolder called GPS. In that folder are 3 small files. They end with .BIN if I remember correctly.
I backed up the nuvi 30's files completely first. Then I started copying over system files from the 50 to the 30.
Once I copied over those 3 little files from the GPS folder from the 50 to the 30, that did it. On the next boot, the 30 acquired a GPS signal and ta-da, DST was recognized. I was good to go. Clock problem solved.
There were no issues with normal operation of the nuvi 30 after copying these files.
It happened with a second nuvi 30!
I own two nuvi 30s because I like the model. With the second one I received, the exact same clock sync problem happened. The fix was also exactly the same. Copied over 3 files from the .System/GPS folder, reboot the unit, done. Clock sync worked after that and DST was properly recognized.
Both units had never been upgraded since they were originally bought, so the firmware was many versions behind. It's possible the firmware update corrupted the files in the .System/GPS subfolder somehow? I'll never know for sure.
I previously owned a 40LM and the clock sync issue never happened, but I bought it new in 2012 and up until the day I sold it I always was on top of firmware and map updates.
I currently own two 50LMs, both bought used, and they never had the clock sync issue either.
Only the pair of 30s I bought ever had this problem, but as you'll notice from that linked discussion above, it's not something exclusive to that model. But it's possible it only happens on some 2011-2013 models?
On a final note, if replacement system files aren't available, the "fix" is to manually set the clock. Back up the gmaptz.img first, then delete it off the nuvi. After that, boot the nuvi and let it get a GPS signal. After that, go into the nuvi time settings and manually set the correct hour. It will hold this setting and the time will be correct. The hour won't change when crossing time zones or whenever DST happens, but at least you've got a way of getting the clock set correctly. Clock sync will still work aside from having to manually set the hour.