2nd cooling fan speed not working

[Calvin Krug]

I just noticed another problem with my '89 200 .Yeah, another one, 
just what I needed.  When I shut it off and the turbo coolant pump 
kicks in, the radiator cooling fan doesn't come on with it.  As I 
understand, it's a two speed system, and it's supposed to come on low 
in this situation.  I checked the resistors, and they seem fine, so 
next step is the motor.  Which terminals are high and low on this 
thing so I can test it?  Or maybe there's something else I should 
check first?

Calvin