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Reply With QuoteUntil i read that you've already opened it to check, my reply was going to be just that, i.e. to look for corrosion. So, the power switch and media card slot both becoming inoperative must be just coincidental.
It may be that the SD slot has some internal corrosion or dirt so give it a good spray with dedicated Electrical Contact Cleaner. You can use Isopropyl Alcohol instead but it's not as good. DO NOT use a product like WD40 or RP7 though. While the cleaner is in the slot don't power the device on. Get and old SD Card and work it in and out multiple times then when the slot's completely dry (blowing air into it helps) see if the card is recognised.
To help you further, i need some more information because i've never worked on a 556s chartplotter. Is this a Mass Storage device (i.e. the internal memory shows in Windows Explorer) or is it a "region-only"device?
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Today, 02:17 AM #1Junior Member
- Join Date
- Jan 2026
- Location
- Australia
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Garmin User. "Can't unlock maps "
I have a Garmin GPSMap 556s which has let me down a few times. First it started freezing up and the power button never worked, had to unplug power cable and re-plug to get it working again.
Now the card reader no longer works, cannot read any SD card and the screen displays "Can't unlock maps " On startup it shows that it has built in Map Aus/NZ Marine Detail g2 Update v2013.0 14.50, but will not load it.
All functions work except I am locked out of the map and the card reader is not working. Have checked my SD cards on computer and they are good.
Have tried with the restore factory settings several times but it made no difference.
I have opened it up and there are no signs of corrosion. Is this too much information,
Am I possible wasting my time and should replace the unit.
Open to any advice, good or bad!
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Today, 05:48 AM #2Garmin/GPS Systems GMod.
- Join Date
- Aug 2011
- Location
- Oz.
- Posts
- 6,396
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- 2503
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