Hello, my name is Rudy , and I do have three Promark 3 units and two of them have problems tracking for satellite!!, I'd tried to update OS and other softwares but still nothing!. I have to say they are 5 years old and are in bad shape for the work they have done. I would like to get some help on this, since i live in the Dominican Republic here is not specialiazed store or tech support for them GPS. Thank you for your further help.