The air conditioner just sits on a square gasket that's compressed with 4 bolts that squeeze the gasket between the roof and the bottom of the air conditioner. The bolts go through the metal frame that holds the filter rack to the ceiling. It's rare but those gaskets do need replacing after years of use.
My a/c leaked when I parked at the curb on a rainy day. The water poured in! When I replaced the gasket I found a low hanging telephone wire had been caught by the air conditioner as the motorhome passed under it. It pulled the gasket out of place. It only leaked when the MH was tilted toward the curb.
You never know, even if you bought your RV new, where it's been or what might have happened to it while it's not in your possession.
Don Ford
2004 Safari Trek 31SBD (F53/V10 20,500GVW)
'09 HHR 2LT or '97 Aerostar MiniVan (Remco driveshaft disconnect) for Towed vehicles
BlueOx Aventa II Towbar - ReadyBrake Inertia Brake System