A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Michael Bradley
Date: 2017 Aug 28, 02:24 -0700
WD40 contains, I believe, silicones, which are insulators. It's good sprayed on the outside of, say, igniton leads.
Silicones on a sliding electrical contact are however bad news - adding extra insulation exactly where better conductivity is needed.
Respectfully suggest you use, on the sliding contact of any rheostat, 'Contact Cleaner' fluid sometime called 'Switch Cleaner'. Obtainable retail in the UK from Halfords.
Good sailing and vanning