[morzh]

The only thing I have to agree with, I found old soldering on coils oxidized (or whatever that dull film on top is) the meter probes do not make contact unless those are sharp neede types.
So when first I get open reading (same happens when I check resistrs) I persist, trying to scratch the film. About 60% of them are like that in my experience. And coils exacerbate the situation as the contacts are flimsy and poorly attached to cardboard, so I am reluctant to really push my probes into it being afraid to break the wire or the contact. So make sure you have the contact when buzzing coils.