How do you see it any other way than that you owe them a refund? Have you ever tried to stay in a hotel room that is 80?
And yes, I’ve stayed in many rooms 80 and above. Not ideal. But open a window and throw on a fan.
Otherwise, why even try to find an a/c tech at night, if you know that it won't make a difference?
A partial refund would incentivise we-tried-our-best problem solving.