Yes, tenants have right to get it fixed if you are not

reachable. In hot summer, making AC working is top priority to them. As long as they can show proof that they have tried to contact you and not able to get you, they will have made the case if this is contested in court. Email can be proof. You often give tenants two phone numbers. If one fails, they can use the second and reach you. As a landlord, you need to check email very often in a day.

If Tenant never tried to contact you, they fixed it themselves. Then, it's their fault. During move-in inspection, you need to educate your tenants what is correct behavior, what is not. So they can follow the right protocol.