This is why you need to remove the coil. Most have never been removed, and this one has forty years of debris behind it. If your A/C system worked fine before you took it apart, then all you should need to do to your coil is clean it and comb some of the fins. If you don't know for sure that your coil is good, it would be wise to take it to an A/C shop to have it tested for leaks. In this case, they are not available new.