If your evaporator coils are made from copper, don’t use vinegar. The acid in the vinegar can corrode your copper coils over time. For aluminum coils, cleaning with vinegar is an okay solution. Always dilute it in a 1:1 ratio with water.
Check your manufacturer’s instructions to see what they say about vinegar.
Overall, we recommend a coil cleaner rather than vinegar. If you want to use a DIY solution, water and dish soap is best.