High Idle Speed - Sometimes

["Scribner" <lscribner@newwave.net>]

I have a 90 Jetta and it sometimes has a high idle.
Idle goes fast, 1500 to 2000 RPM,  just about the time the fan for the
radiator turns on.
Is this normal?
If I disconnect the idle stabilizer solenoid, the idle drops to 1000 rpm or
so - about right.  Plug it back in, and the idle stays low.  If I disconnect
the two temperature switches in the cooling lines from the block, no drop in
idle speed.
Car almost always has the cooling fan come on 10 seconds after the ignition
is turned off.  Is this normal or part of the problem?
TIA,
Tony