RT5 Crossover Problems

I have a set of RT5 Bookshelf speakers that I have had for a while. The tweeters stopped working in them so I tried to figure out why. I found that the tweeters are fine because they will play when hooked up to other speakers. So I figured it was the crossovers.

I replaced the (not sure of the proper term) cap for the tweeter on the crossover and reinstalled them.

Tweeters still did not seem to work. So I tested further.

I unhooked the midrange and hooked the tweeter up to its wires and it played fine.

I kept the midrange unhooked and hooked the tweeter back up where it belonged and it actually was playing, just very very quite. You almost have to have the reiever on max to hear it well.

So here is my question. What component on the crossover would cause the tweeter to play at such a low volume if not the cap for the tweeter itself?

Thanks for any advice you have.