Posted 5/17/2022 06:13 (#9663596 - in reply to #9660395) Subject: RE: $100 to first right answer/ Case 1200pt fertilizer pump issue
After reading all this and it puzzles that only affects with vac fan on. I wonder if you don't have a cracked valve body. Internal crack that you can't see. Wouldn't be hard to swap a multivalve body if the dealer has a planter on the lot to do so.
Maybe I missed this in the comments but just a 15 minute swap would eliminate a lot of unknowns.