Thanks Rainier
I have now fitted the Garmin GPS 175 but not yet flown it.
Wiring and set up has been done as per the Garmin 400/500 Arinc integration guide and things are looking promising.
The Garmin test page shows half left indication but nothing on fly up / down, the map gives a line from present position to Garmin HQ. Any idea where I might be wrong with the vertical nav ?