Does it kill an A/C to run it off a generator?

plug in an in line veltage meter (about $20.00). MOst 120 volt AC appliances operate just fine on 120 volts plus or minus 10%. If the genny will hold 107 volts or more it should do no harm. Unless you MEASURE the voltage you're just guessing. On a related matter though, MOST generator manufacturers do NOT recommend running their generators at full draw for long periods of time. The harm in that case is to the generator, not the AC.