Where is the best place to find assistance/maintenance for a senior's air conditioning?

Are you asking if there is ASSISTANCE for seniors for AC?
if so you can ask at your local Senior Service Center or Area Agency on Aging and see if there are any programs that can help provide AC. Or at the least window fans that might help with air circulation.

If I have this wrong you might want to give a bit more info

Air conditioning? What???

If you're in the US, try FindHelp.org for local resources.