I have a through the wall A/C unit. Unit is about a year and a half old. It doesn't seem like it ever worked properly. It cycles on and off quite frequently, and on hot days really has a problem cooling the room down. The prior owner replaced the sleeve. The a/c doesn't go all the way back into the sleeve. There is probably 4 inches of gap between the where the a/c stops and the sleeve ends. Could the a/c not going all the way back to the end of sleeve be the reason for the "lack of performance" of the unit, or do you think that I just need to replace the unit?