Seriously, what can go wrong with a compass? Apart from all those jokes about what happens when you place two compass close together (both will be wrong!), let's run through the different scenarios:

=> Compass smashed. Fairly easy to see which one broken and not

=> Compass needle is stuck and can't move freely. A 10 second test will show you if this is the case - just rotate the compass while you hold it horizontally

=> Compass needle is completely de-magnetised. Highly unlikely. Rotate the compass while you hold it horizontally, and you'll see

=> Compass needle has changed polarity (north points to south). Rare, but there are at least one report here on ETS of that happening. Use other indicators to tell which is which. If you can see the sun you can tell which direction that absolutely isn't south.


If the compass needle is magnetic and can rotate freely it will point to magnetic north unless there are other magnetic objects really close to it (such as the other compass). Period. There's no way a compass can be pointing consistently, say, 45 degrees in the wrong direction. You need human navigation errors for that... (such as messing up when finding out which heading you should use).