Found a magnet near my compass

[Marco Flamingo]

I've had some concerns with how close my compass is to my Garmin EchoMap MFD. It was installed by a local boat yard and I thought maybe they had determined that the screen doesn't have much effect on a nearby compass.

Yesterday, I was setting up the Garmin WiFi to work on a laptop to be used on the upper helm. I was opening a little door on the MFD that holds a mini SD card inside. I noticed that the door snapped shut like it was held closed by a tiny magnet. The little door is closer than a foot from my compass. Sure enough, opening and closing the door made a 4 degree difference in the compass reading. Today I'll watch the compass as I turn on the Garmin and see if that has an effect. Maybe remove the magnet from the door? Seems like an odd closure mechanism on an MFD when there's a 99% chance of a nearby compass.

 

[RT Firefly]

Greetings,
Mr. MF. Perhaps the yard was unaware of the magnet in the device OR didn't care. Like, who uses a compass anymore (I do).

 

[TG]

You can check the documentation for the Garmin and it will list the Minimum Safe Compass Distance. A quick look on line indicates somewhere between 21-25 inches depending on model.

 

[rgano]

It is probably a spiral wound spring in the door hinge of the Garmin that is slightly magnetized.

 

[Frosty]

You can check the documentation for the Garmin and it will list the Minimum Safe Compass Distance. A quick look on line indicates somewhere between 21-25 inches depending on model.

Just as a note: My Raymarine Axiom manual does the same, but there are different distances specified for the various sides of the chartplotter. I never looked up my previous (Garmin) as I had not installed it.

 

[MYTraveler]

The little door is closer than a foot from my compass. Sure enough, opening and closing the door made a 4 degree difference in the compass reading. Today I'll watch the compass as I turn on the Garmin and see if that has an effect.

You probably know this, but in case you don't, the affect that magnet will have on your compass will vary depending upon the direction of the magnet from your compass, relative to magnetic north. If in line with magnetic north -- no affect at all. If, say, 10 degrees out of line, perhaps only 4 degrees. If 90 degrees out of line with magnetic north, perhaps much more than 4 degrees.

 

[Comodave]

Yes, deviation does change relative to headings. Sometimes wildly.

 

[Blissboat]

It's unnecessary for an object to be magnetized to affect a magnetic compass. Anything ferrous in close enough proximity will move your compass card.