My 99XL 45 and my 01XLII Marathon has 2 of the cruise airs behind the front bumper and the 3rd located in the 1st bay on the curb side. I found running 2 out of the 3 with the invertors works fine. I think the trick is to try and start the day keeping the bus cool, don't wait until it's hot inside, it won't cool it back down.