Tenant installed window AC in utitlies furnished rental

[Cheryle Patterson]

I have owned a 16 furnished room (dorm style) rental property for 14 years and never had a tenant do this.  We rent the rooms for $395 per month and it includes power, water, sewer and garbage service. We keep the A/C set at 72% and our current tenants have never complained. I rented 2 rooms out last month and they immediately started demanding lower tempature. I have lowered the thermostat to 70 degrees and it is running all the time. IMO, it is freezing in there.  Now, one  of them installed a window AC in his room. I called and told him it had to go. He told me that there is nothing in the lease that says he can't have it and is refusing to remove it.  I told him my lease doesn't say that he can't park a car a garage in the living room but that doesn't give him permission to do it.  Says he will sue me if I file for eviction. Any ideas?