Tried dielectric grease on my Cessna 172 battery terminals and now I'm chasing a charging issue
Last week I cleaned up the battery terminals on a 172 and figured I'd put a light coat of dielectric grease on them since everybody swears by it for corrosion. Two days later the owner called saying his ammeter was bouncing all over the place and the battery was draining. Turns out I slathered it on thick enough that it got between the terminal and the connector, and grease doesn't conduct (yeah, I know, rookie move). Cleaned it all off, torqued everything to spec, and the charging system went right back to normal. So how thin are you guys actually applying this stuff, or am I better off just leaving terminals dry and keeping them clean?
Heard about this exact thing from an A&P buddy of mine who's been turning wrenches for 30 years. He said he did the same thing early in his career and learned the hard way that dielectric grease is an insulator by design, so it should never go between the mating surfaces. The trick he showed me is to put a tiny bit on the outside of the connection after it's tight, just to keep moisture and acid off the metal. He barely even uses a pea-sized amount for both terminals, and most of that ends up on his rag anyway. Honestly after hearing his story and reading yours, I just keep my terminals clean and dry now and check them at every oil change. Clean and tight beats greasy every time in my book.