Corroded connectors are a primary cause of problems in automotive, marine and machinery operation.
A liberal spray of CorrosionX cleans and protects against further corrosion. With polar bonding the product creeps into wiring harnesses. Far superior to WD40, and approved by Boeing, Pratt & Whitney, Cessna aircraft, Caterpillar Marine.
Always have a can handy. Works well on PC USB connectors as well.