Looking for a Garmin?

[Normagain]

Do a Google search on "740s compass" and you will find plenty of discussions on the subject. Most say it is the magnetic door where the SD card goes which can interfere with the compass though it could be electromechanical (electromagnetic?) interference from the screen or somewhere else in the Garmin. I remember one of my VHF radio instructions said the same thing. They are probably just trying to cover themselves from liability due to inaccurate compass readings. Just move the unit around with it on when you are mounting it and see if the compass reading changes. Most seem to say it is not an issue. Garmin usually answers the phone from my experience and is very helpful so you could call and ask.