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'The connections were changed' - do you mean that custom modifications were made to it in any way?
I think the best you can do (though I'm not quite clear what 'flashing lights' would mean - is that 'snow' or static on the screen?...) at this point is to remove the battery/batteries and other power source from the Garmin device, and leave it on a warm dry dust-free shelf for overnight, then after that put the batteries back in and see if it works.
How old is the Garmin 541? in months or years since you bought it.
Has the Garmin 541 been dropped or otherwise subjected to mechanical shock(s) in its lifetime?
Has the Garmin 541 been operated in or subjected to, temperatures below 32 degrees F (freezing point) or above about 100 degrees F ?
Has it ever been subjected to a humidity higher than 85 % or gotten wet ?