I'm not sure with the newer GM's but the older GM's had a fusable link (actually it was a fuse) inline with the compressor which would fail if draw on compressor ( such as low coolant) was too high. Soooo just adding coolant may not be enough. The fact that it happened overnight so to speak would make me think there may be a fuse problem in this solution also. If we put a new fuse in and it kept blowing then we knew the coolant was low ( sometimes we just changed the fuse and all was ok). This may help...I hope it does.

Icesailor

82 300D T
66 TR4A IRS
66 TR4A Solid axel