just use carb cleaner. electrical contact cleaner can leave a residue so I would avoid that.
Give it a spray them rinse gently with warm water and let it dry. DO NOT TOUCH THE METAL ELEMENT with anything. don't use a cotton bud on it like some places recommend.
spray it, rinse it, dry it and put it back on.
you can get carb cleaner in Halfords for about 5 quid a can.