Garmin 496 interferes with magnetic compass

[N999BT]

I have a problem in that it seems that my Garmin 496 has become magnetic and is causing my compass to indicate more or less 300 deg all the time. Also, my trutrak autopilot is affected, I just do not know to what degree, because it is just above the 496 as well.

I have tried many things to try to isolate the problem; power, no power, unplugged from external antennas, etc. The antennas, (GPS and XM) are remote to the unit and are not a factor. The compass swings radically when I put the GPS unit in its panel bracket. I took the battery pack out and it appears that the battery pack is the culprit because it makes the compass swing when you wave the pack near the compass.

Has anyone seen this before? What can be done about it?

[lucky]

just as a sanity check just to make sure there isn't something really wrong with the one you have. Borrow someone elses and see if it does the same thing. I'm suspicious since I've never heard of this before but I've seen a lot of different installation variations.

[N999BT]

I will try that. I really think it is mine - somehow I magnetized the battery pack sometime in the past. I don't really look at the compass all that often when I fly, but I know it worked about a year ago because I calibrated it.

[N999BT]

After experimenting with a different panel location away from the 496 and discovering that the problem did not change, I have concluded that something is REALLY magnetic in front of the firewall. It is also possible it could be EGT / CHT wiring, since there is iron in those wires.

I took a handheld compass and found some weird things just in front of the firewall on the right side, but it is hard to figure out just what it is because I have my battery mounted on the engine mount there. In that vicinity is the battery, the left mag, and the master solenoid mounted on the firewall.

I am still baffled.

[PJSeipel]

Well, your master solenoid will be magnetic when the coil is energized. Does the compass read properly when the master is off?

PJ Seipel
RV-10 #40032

[Norman CYYJ]

A lot of the antennae for these portable GPS's have magnets in the bottom of them. Remove the magnet and your problem may go away. Same with the WX antenna.

[N941WR]

Could we see a picture of your panel?

I installed a Dynon D100 EFIS in my panel and a 496 for navigation but never installed a whiskey compass. My reasoning was that the D100 has a battery backup, as does the 496. The 496 is my primary (only) means of navigation and should I lose electrical power, its internal battery will get me home.

BTW, this is legal as the Dynon provides a magnetic direction indicator, not that I want to start that discussion again.

PS. I'm VFR only so this works for me. If you are IFR, that may exceed your comfort level.

[pierre smith]

I told you guys about this problem last week. I have both my 496 antenae on the glareshield and my vertical card went T.U. and it's on the way for repairs.

Thanks,

[N999BT]

I think something in my engine has become very magnetic. The problem does not seem involve any electrical device being on or off. When I go around the engine, there seems to be something that has a strong magnetic field that rapidly changes direcection with small movements of a compass. It is near the back of the engine. I have heard from various people that it could be the crank, or the cam, ...sigh. I guess I will just take the compass out of the panel and use the AFS compass only and if I really need a backup, drag my backpacking compass out, and my protable Gps, and ask for vectors. Hopefully the ALL the elecronics don't fail at the same time.

[Norman CYYJ]

Had a friend that had problems with his compass. Turns out that somehow there was a strange magnetic field forward of the firewall. He eventually had to have the entire plane deguassed. that cured the problem, but it wasn't cheap.