The Cessna 120-140 Association Forum

So I'm working on my Ford Ranger multi-function turn signal and I see there is a bunch of grease all over the internal copper contacts. Reminded me that I have a tube of Dow Corning 4 in my hangar that an A&P had me buy years ago and I don't recall what it's purpose is. I think he said to use it on the silicone parts of the ignition harness? I figure it's non-conductive.

It's called "dielectric grease". Used to lubricate and prevent corrosion (by excluding moisture) on switches, connectors, light bulb sockets, etc. It is non-conductive in that it won't short all the pins on a socket together, but it will not insulate an otherwise good connection, either. Your A&P may have wanted you to use it on the connections between the ignition wires and the spark plugs.

Ah, that makes sense. The old Aero-Lite ignition harness was a little tight on the plugs. My overhaul with new Kelly wires aren't so tight so I never thought to use the stuff. Thanks!