Possible Clues:

• Central cooling systs
• Room coolers, for short
• They may rest on sills: Abbr
• They're rated in BTUs
• Summertime coolers, casually
• Some auto options, briefly
• Carrier products, briefly
• Coolers, briefly, that span two words in the nine longest answers
• They might be set in windows: Abbr
• Temp. reducers