Speaking with an electronic systems designers' hat on, the idea of spraying WD-40 around electrics willy-nilly doesn't strike me as wholly wise. As the MSDS makes clear, WD-40 is nothing more than a mixture of white spirit and mineral oil. Neither is particularly good for either the galvanic properties of conductors or the long-term insulation properties of many plastics. Quite where WD-40 acquired its stellar reputation is a mystery.
If you want to disperse water and keep condensation out of an engine bay, a silicon/PTFE spray will do the job effectively. If you want to clean low-voltage or low-current connectors, propanol and a toothbrush works well.