hi Steve, the navman 3100 series was discontinued and replaced by the Nothstar 310 series but this too has been discontinued and are no longer available. The issue was the glue that the contact strip was attached to the LCD screen
which has intermitent contact given heat and humidity. I managed to get a new repeater being the nothstar 310R display on ebay from Canada
just to save me replacing all the intsruments in the short term. GOOD LUCK!!
All the Best