*Fuse 44 was burned. (F16 was missing, but F41 and F43 were ok). Forgot to put that in the orig post. So the pressure can swing that high when the aux fans aren't working! (not like R12) And this is just Indiana summer.
*This owner lives on a wooded lot. Can hardly see the house for all the trees. And the ML sits for long stretches (underhood rodent damage). So I think you're spot on again about the tree debris in the vents.
*Any suggestions on finding that specific update doc in WIS? I posted another thread in this forum about my difficulty navigating WIS (the 'Help' in WIS doesn't offer much substantive help). WIS was designed to dovetail with DAS in SDS, not just as a stand-alone information source. Unfortunately I don't have SDS (big bucks!).
*The bad news is that this customer went away mad, so I may never get the opportunity to check out this new information. Thanks just the same.