We recommend replacing both the indoor and outdoor units of your A/C. However, there are exceptions to this. For instance, if your unit is still under warranty, your manufacturer may provide you with a new and compatible unit at little or no cost.
But if it’s not under warranty, it’s best to replace the entire system at once. The indoor and outdoor parts of your A/C unit were designed to work together. Pairing them with different models may result in problems.