These units can often be refurbished- loosen the nut on the terminal so you have some access to the inside. Blast same liberally with WD40, shake, rattle, roll, repeat. Let sit for a day. Then intermittently apply pressure to the end that screws into the block. Monitor the resistance with a VOM. The business component of this part is a rheostat that moves as the pressure increases and changes resistance. I've had good luck with this technique, and the fix seems to last.
Actually this fix works well on all electrical components where corrosion/ goop accumulating twixt contacts is the problem.