Not sure about the AF theory. I have a Rule bilge pump and float switch installed in 2007 that’s still going strong, knock on wood. After seeing it frozen in an inch of ice the first winter (From condensation, not leaks. Boat is shrink wrapped.) I started putting AF in the bilge as well as placing a half dozen DampRid buckets around the cabin during winter storage. Batteries are always completely disconnected in winter. Sometimes it’s pink AF from the water system, sometimes green or purple from the engine, and sometimes an ugly mix of whatever‘s left in the bottom of each jug.
My backup bilge pump is Johnson, installed around 2010 or so and always sits above the AF because it’s higher in the bilge. It’s still holding up too, but is operated only when I check it a few times each season. My impression when I bought it was that Johnson might be better quality than Rule. Figured I’ld make it the primary whenever the older Rule pump expires. Anyway…
Manufacturer quality control issues and/or a streak of bad luck seem more likely to me, but if it’s happened across multiple pumps and multiple brands though, I don’t know…. Did all three pumps fail in the same way? You said it’s “toast“ but the wiring and switch are OK. Could the fuse on the bilge pump circuit be defective or oversized?
Edit: I always use Propylene Glycol anti-freeze. Never alcohol.
