Sounds normal to me. If you had neglected the air filter, you could have a lot of crud on the fins of the evaporator coil. If that is dirty, it reduces the efficiency of the unit, and the accumulated dust is a good place for smells to originate and things to grow. So, it might be worthwhile checking and maybe cleaning that if necessary. You need to do this carefully, since if you bend the fins, you decrease its ability to function well.