Yes, a new air conditioner for a Rental Property is considered an Improvement, which is entered as a separate Rental Asset from the Rental Summary page (see screenshot #1 below - click to enlarge).
Rental Improvements are in the same class as the property itself, depreciated over 27.5 years. For this reason, choose "Real Estate Property" as the subcategory for this asset (screenshots #2 & #3).
The easiest way to find Schedule E for Rental Properties in TurboTax is to use the Search box at the top right side of the TurboTax header. Enter "schedule e", hit Enter, then click "jump to schedule e". This will take you directly to the start of this section.
Or go to My Account >> Tools >> Topic Search. Type in "schedule e", then click the topic in the list.
Note that you may qualify for the Safe Harbor Election, which allows you to expense improvements under $10,000 in certain circumstances. If you chose this election, you will enter this improvement as a Rental Expense (repairs, for instance) and not as a rental asset. Screenshot #4 shows the page where you are asked about this election.