I don't know your specific model compass, but the ones invariably
fitted to fill a hole in the dash on cars is a simple flux gate type.

Your vehicle should be away from any external source of magnetic
interference (in other words don't do this under a steel bridge or next
to an electricity sub-station).

With engine running, accessories like radios etc running, push the
button and hold until the needle starts rotating around the face.

Release the button and wait till the needle stabilizes.

It should now be pointing more or less North.

If it isn't, go to your nearest aviation supply house and buy a sucker
type "Inoperative" cover of the correct diameter and stick it over it.

At least then you will have a conversation piece, and even when working
they aren't much of a compass.

Tony Smith

Stop pushing the button and concentrate on your driving.  You've spun out.