HVAC issue with tenants.

[Yengkong Sayaovong]

I have called a contractor out to fix the AC unit twice within the past month. I knew what the issue was but I didn't want to just blurt it out without any proof that they are turning the AC off when leaving the house. 

I have asked the first time and they said they never turned it off. I paid for the AC fix twice already. The 2nd time, the AC contractor told them the AC unit is working fine and not broken like they said. Their issue was that it wasn't coming on fast enough for them. They told the contractor that they turn it off when they leave the home to avoid paying high electric bill. Contract between me and them states they can't turn off AC unit but they can turn it to a temperature of their comfort. Contractor says they can leave the AC on low but can't turn it off, especially in 90+ degree weather.

I got a text today asking if I can pay half the electric bill otherwise they won't leave the AC on when they go to work. HVAC is a landlord responsibility in my state so if I already took care of it twice and the contractor told them the issue is that they keep turning it off, would I have to keep paying for the AC unit or can I tell them it's their responsibility to pay the contractor or pay all the electric bill? Contract states they pay electric bill. They've only been a tenant for 2 months.