How does a compass work and why I don get accurate reading in my car?
The main problem is that your car is made with a lot of steel, which not only can act like a magnetic shield, it can become slightly magnetized. Also high current electrical items, like your headlights and blower fan, they draw a lot of current, and current flowing thru a wire makes a magnetic field. In my car I can make the compass move 30 degrees west when I switch on the blower. The best place to mount the compass, for best accuracy, is right above or below the rear view mirror. That’s where it’s placed on small airplanes. I’d see how far off the car’s magnetic field affects the compass by starting with the compass in my hand 30 feet ahead of the car and due north. Then approach the car slowly and watch the compass indication. Take the compass all the way to the top of the windshield. If it’s drifted more than 10 degrees or so I’d for get about using the compass. Then turn on the blower and see how much farther it drifts. A higher-tech approach is to get a GPS navigation gadget. The
