When maintaining mini-split ACs, you need to check them separately. One common issue with mini-split AC is the gradual degradation of the line-set insulation. Rodents may sense the presence of moisture and bite into the insulation of the line-set to get to the water. It’s more likely to happen if you place line sets horizontally, instead of vertically against the wall. Brittle or chewed-up insulation should be replaced immediately to maintain the performance of your AC unit and prevent corrosion.