Yes, pitot heat power will interfere with the Garmin magnetometer mounted on the ADAHRS shelf. I ran a power wire in the "bundle" in the wing with a ground to a rib by the pitot - failed miserably. Then I ran a ground wire (not twisted at this point as Walt has recommended) - better, but still failed. Then I rerouted the ground farther from the magnetometer, twisted it around the power wires(s) near the magnetometer and got better results. It still fails Garmin's interference test for about 3 seconds during power up and power down, but I called it a victory.
Is there any reason not to run coax for pitot heat? I'm guessing it would be much better than twisted pair.
But (in either case) this only works if the ground return is not connected to the pitot tube or its mounting harware. You need the return current thru one wire to equal the feed current thru the other.
I'm a few months from needing to worry about this and haven't studied it yet but this confuses me a bit. You DON'T want the ground connected to either the pitot tube or its mount?!?
I'm a few months from needing to worry about this and haven't studied it yet but this confuses me a bit. You DON'T want the ground connected to either the pitot tube or its mount?!?