The fire started around 4 p.m. Friday at the Baker Auction and Reality business in the 500 block on North Weinbach.
The owner was right next door at another business when he noticed the A/C was on fire.
Flames shot up in the attic.
He was able to get all of his employees out. The damage was minimal inside the building.
The owner say the air conditioner was recently installed. They will be open on Saturday.