Suburban brand wall unit w/ ac & "sealed box" LP burner. Mod # DL11-0912ET. Weak flames steady "draft-wize", but surge up and down, even though manifold pressure at burner valve outlet steady at 10" wc. Cleaned burner, found strange "burner air" adjuster (which is more like a nozzle-venturi), installed new flame sensor which helped some but system "locks out" to safety purge daily. 240 vac w/ good ground.------------ What next guys, not a whole lot of theise units around here, HO works for elect. power co. and ordered this item from a catalog. Hope someone can help us out.