Probably not enough that you can tell it with an ohmmeter. What does change
is the inductance, pretty hard to measure with cheap equipment.
Best way to test it is to put one in that you KNOW is good and see if that
helps. While leakers and ones that show different resistances (or open)
definitely won't work, haveing the correct resistance does not mean they will
work. There are other things that can be wrong with them, for example the
magnetic core being stuck or loose.

If you can't lay hands on a known good one I might be able to loan you one to
test with. e-mail me offline.
--
George Downs, Bartlesville, Heart of the USA!