We have encountered rooms where the A/C doesn't work well.We simply insist it is fixed that day, failing which they must transfer us to another room, failing which we walk out.
You are paying extra for A/C that works.
Many hotels have a "bad room" - there may be a smell from pipes needing repair or poor A/C or noise.They know that some guests will accept this without protest, so the room is used.Its up to you.

How can you leave the hotel even if they can't/won't give you another room with working a/c? I'm sure they'll end up charging you anyway-unless they agree not to? Many have a policy where they charge you if you leave early.

In my experience, Europeans view AC as a way to make a room less hot--not as the instant cool blast that we are used to. It is extremely difficult, in my opinion, to find a hote that will have AC that is up to US standards--but your best bet is a business hotel...charmless, sure, but when it's hot, you need it, and in the summer, when you need it most, business hotels go on sale.

Lack of decent air condirioning in Europe is the main reason why I never travel there in the summer months. I love the Fall in Europe. Much cooler, less tourists and less annoying body-odors to inhale.

Nothing is more nauseating then an unbathed fellow traveller, in polyester or wool clothing in 90? temps. You have to remember that no one is as obsessed with cleanliness as the Americans.

Need to add my 2 cents to this discussion and concur with the answers. We were in Vienna during the hottest week in 52 years -- it was in May -- and although we try to stay in local hotels opted for the Hilton am Stadtpark because of A/C which, as most posters have noted, didn't succeed in cooling anything. For this, and a host of other reasons, avoid the Hilton am Stadtpark (there are two Hiltons in the City) as it is rundown, with only a marginally acceptable breakfast buffet, and gives the chain a bad name

I think Alise has it right. I was in Greece for two weeks where it was in the 90's every day with a clear blue sky and the bright sun beating down. One of the guides in Athens said she only has an air conditioner in her bedroom and had just turned it on for the first time well into the hot spell.

My worst experience was in Olympia where the hotel was said to be modernized for next year's Olympics. The AC was definitely controlled by the hotel, which shut it off completely during the night. One woman said she went outside and sat on her balcony at 2:00 am with no clothes on at all. No one admitted to having seen this, however.

I find the air conditioning in most US homes and businesses to be set too cold! I freeze. Why soooo cold?

Your body does adapt to what you are accustomed to. I grew up in the US deep south, and we did not get A/C at home until I was 8. There is no way now that I can tolerate the same indoor temps that I routinely did then, and my young son can't either. We are currently engaged in a major battle with the local school district over putting A/C in schools now that the year is longer; kids who are used to having A/C at home cannot concentrate properly in a classroom that is 96F.

That said, I'll agree that American businesses tend to keep their premises too cool in Summer. The reason is wishful thinking, I believe; they are setting it for crowds. The more people in a building, the lower you have to set the temp to compensate.

I remember a few yrs. ago, at a hotel in Florida, I went to take a photograph in my hotel room and found that I could not. We had just come in from outdoors, and the change in temp fogged up the inside of the camera lens.

I love my room to be at about 68 degrees.

Brrrrrrrr! I like my room at about 78 degrees.