2004 P32 condor, parking brake problem gray switch blown

Hi, I got a problem with this parking brake gray switch, I replaced that switch five times now, the switch blows, crack or pop the head resulting an oil leaking so engaged the parking brake. And it goes faster and faster I meen first time maybe a year before the problem and now, I just changed it run 45 min and blow  again.. I don’t know the problem if it is because too much pressure at the gray valve ? If it is how reduce that pressure .. I am lost on this one 

   Help anybody 

… Daniel