[jsb5717]

Do you have the Whisper Quiet system or do you have interior access to the plenum? Whisper Quiet makes it a little more challenging but I would be tempted to run a borescope up there when it’s leaking to see if I can spot the source.

Also, with Whisper Quiet system you don’t have the interior nuts to tighten the AC to the roof via the through-bolts. The AC anchors to the roof via lag bolts that have to be tightened from the roof after removing the cowling. Maybe they just need a little tweak to better seal the thing to the roof. Just don’t over tighten them since they could strip.