Denying use of common facilities (Power Backup) by Association

Q: Our builder has provided Generator Backup for lift, common areas and individual apartments (1 KVA for 2 BHK and 2 KVA for 3 BHK). The same is mentioned in the brochure and sale deed. I considered this as a key feature when purchasing this apartment and my flat is on 5th floor. However, the association is denying generator utilization in case of power failures and has made a rule that generator will be turned on only from 5 pm - 9 am). This is wrong considering every flat owner has already paid for generator and is paying for diesel in monthly maintenance. Our association is registered under Karnataka Owners Association Act. Is there a legal way to stop is harassment by association? Are there any provisions of law that can help me in this case.