N

N999BT

Well Known Member
Patron
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?
 
use a different garmin handheld...

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.
 
Magnetic Garmin 496

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.
 
Its not the 496

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.
 
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
 
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.
 
Do you need a magnetic compass?

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.
 
Well sonofagun!

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,
 
Its not something obvious

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.
 
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.
 
To close out this thread

I finally came to the conclusion that mounting a compass in my panel was not going to work. I have tried several spots. I ended up mounting it about 8 1/2 inches back from the panel on the right side canopy rail. It works fine there. I guess that there was just too much magnetic stuff in the panel, in front of the firewall or something. Anyway, problem solved. Thanks for the replies. I just heard about a guy at the airport who ended up degaussing his airplane only to have it become magnetic again in a couple of months.
 
Just for ha ha's, try putting a steel (not stainless) plate between the suspected source (the closer to the source the better) and your compass.

A few years ago in an earlier life I had to ship very strong magnets to Eruope via air which gave my customer's customs broker severe palpitations. There is a published standard somewhere that allows magnetic things to be air shipped if when spun around at a distance of (something like) 30' away from a sensitive compass the compass needle deflects less than (something like) +/-2 degrees. After carefully packaging in a particular sequence so that the lines of force were directed as inward as possible, a military issue compass swung wildly side to side when the pallet was spun in place. It was amazing to see. We just kept adding steel to the box until the compass calmed down sufficiently.

I've never seen anybody suggest a steel plate to help out a compass in an aircraft, it may do as much harm as good. The suspected source may also need its magnetic characteristics left as-is (not shaped, funneled or distorted by a steel plate).
 
It came back bad.

My vertical card, that is. I mounted it to the roll bar brace so it could freely dangle, as per the instructions. The supplier called me and said that it was out of warranty...well...duh. For $150 something I could get another one. No way, I'm going back with a good old American made whiskey compass instead of that Chinese made junk. Both my 496 antennae are on the right hand side of the glareshield so it seems 18" is not enough? Or is it?

Sheesh,
 
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