Marine Electronics Questions? Ask a Technician for Answers ASAP
The only real test you can do is connect another chartplotter to your GPS antenna.
If it doesn't work either, the either the antenna has a fault or there is a problem with the wiring.
Sometimes these problems are just caused by a loose wire.
If it does turn out to be a fault with the antenna, then you can replace it with any NMEA GPS Antenna, e.g. the Raystar 130:
On the Raymarine. Orange is Rx Data +, Yellow is Rx Data -
Another test option would be to borrow a chartplotter from another sailor.