Strike that - it was nearly two years ago. The freezing and subsequent thawing of the unit in the hot sun led to a giant stain on the ceiling in the office study-o.
I left the stain for ages as if little painting gnomes would come and magically fix it in the middle of the night. After waiting a reasonable period for the little slackers to show up, the time came to finally say goodbye.
At first, I tried latex primer. But for tough water stains, there really is no substitute (no redoing later) than oil based.
A little flat white ceiling paint (I keep a quart on hand now just in case), and it’s as if the A/C problem never existed.
Someone should check on those gnomes. They’ve been missing work a lot lately, and I suspect it may be a drinking problem.
Oh those lushy gnomes!
I hope you addressed the cause of the water stain. Hate to see it re-occur.