[GarySP]

Hi,  First thing I would try is pulling the cap out of the chassis and giving it a good washing.  I have had good results putting the unit in my dishwasher with the plates opened out  and running it through a cycle.  Then put it in a very warm oven, or in front of a space heater to completely dry it out.  Once you're sure surface corrosion and dirt aren't the issue you can concentrate on plate spacing.  Remember to lightly lubricate the pivot points before re-installing it.  Good luck. Gary