4000S idle stabilizer valve

[Dave Fain]

Actually this has to do with a 1985 VW Rabbit but the engine is pretty much
the same as a 4000S so maybe you guys can help me.  While I was looking for
the source of a massive oil leak (it was the O ring that goes between the 2
halves of the oil cooler), the idle stabilizer valve suddenly began
humming.  The engine was turned off and the only way to get it to quit was
to pull the plug.  Any idea why this thing would spontaneously turn itself
on?  We got our first snow night before last and the car stays outside,
maybe water dripping into a relay or something?  Nothing else electrical
appears to be turned on.
thanks,
Dave