Often the filters will need to replaces or cleaned. The AC components get dirty over time and would need to be cleaned. As you mount the unit on the wall it could suffer from uneven mounting which could affect how it works. Often the filters will need to replaces or cleaned. The AC components get dirty over time and would need to be cleaned. As you mount the unit on the wall it could suffer from uneven mounting which could affect how it works. Often the filters will need to replaces or cleaned. The AC components get dirty over time and would need to be cleaned. As you mount the unit on the wall it could suffer from uneven mounting which could affect how it works. Often the filters will need to replaces or cleaned. The AC components get dirty over time and would need to be cleaned. As you mount the unit on the wall it could suffer from uneven mounting which could affect how it works.