Barkoff - I had a similar problem right before I took off.
There are a couple of things to check.
1. There are four screws inside (Phillips) Remove them
The cover is off, and inside there are four screws in the corner. Insure they are snug (not torqued down). The unit shouldn't move when you wiggle it.
2. If under the cover there is an intake side (where the air returns to the AC) and an output side (where the cool air exits). Between them is a piece of insulation - it's generally wedged in place. Make sure that the piece of insulation is wedged in place. That's where Newman Fulltimer is referencing above.
Mex is correct. Initially when you turn on the AC, the fan will blow immediately and it may take a few seconds before the AC starts to cool. if you don't hear the AC run, then there's other issues.
believe it or not, its easier to tell when the AC unit is cooling by being up on the roof with the cover off and the AC unit turned on. Initially you'll hear the fan, but when the cooling part (Compressor) starts, you'll hear it kick in - a subtle buzzing sound.
Good Luck!
