" The simple answer is Yes logically, BUT... " – Javier, Technical Director from Smart Mechanical

Can I just replace my outside AC unit?

The simple answer is Yes, but I do not recommend that you only replace the outdoor unit.

It really depends on SEER Rating of your indoor coil. Your old coil's SEER Rating is probably 10 SEER or 12 SEER, and the SEER Rating of outside unit that you want to replace is 15 SEER.

If you just replace the outside unit of the 15 SEER for the indoor coil of 10 SEER, you will only get 10 SEER ability of capacity in Air Conditioning.

As results, we recommend you to replace both a indoor coil and the outside AC unit together when you replace the outside unit. The SEER Rating has to be matched between the indoor coil and the outside AC unit.