tenant says AC not cooling house enough and upstairs hot

[Fernando Domingo]

Hi BP community!

I purchased a house in metro Detroit, MI area that was unoccupied.

The house rented in May and now it's July and and the tenants are complaining that the AC doesn't  cool the house enough. At first they said that the it would go below 70 when set at 68 and they say that the upstairs of the bungalow is unbearably hot.  

I had an AC guy out there who said that the AC was working. He told the tenants that putting a window unit upstairs would be an option for upstairs.

At this point I paid for someone to come out and basically do nothing and now the tenant is asking me to provide a window unit. I let him know that I would give him $50 toward a window unit if he wanted to buy one himself, but to pay for someone come out to tell me the AC is find after being told that it was fine during the inspection of the house when I purchased it doesn't make sense to keep spending money.

Tenant is now saying that the AC guy didn't do anything they asked him to go upstairs, but he wouldn't. He told them that Bungalow houses are old and the upstairs was meant to be an attic. If they want the upstairs to be cooler they would have to put a window unit in. He also told the tenants that the house had no insulation. 

The tenant said that the the unit isn't big enough for the house.  I'm not sure if the AC guy told them that though.

Questions:

Would you buy window unit?

If the AC unit isn't big enough for the house shouldn't that be mentioned in the inspection during purchase?

Since the house doesn't go below a certain temperature when set on 68 degrees are there any suggestions?

Any help with this is much appreciated.