Mercedes: Magnetic Fan Clutch wont engage, fan clutch, fuse box

Question
QUESTION: The magnetic fan clutch (on my 1993 190E Mercedes) won't engage.  I disconnected at the wire and put 12V and it engages, so it does work.   Is there a relay that powers this clutch or sending unit?

Thanks,

Luis Delgado

ANSWER: Luis,
Does it engage when  you turn on the AC?
Robert

---------- FOLLOW-UP ----------

QUESTION: It does not engage when I turn AC on.  I did change soleniod switch at head.

Answer
Luis,
I would locate the fuse box and then check the lid for the fan circuit. Fuse tips get a little corrosion and do not make good contact. If the fuse is a bullet type with aluminum strips, they are notorious for bad connection. Replace aluminum units with copper if you can find them.. The copper sockets need to be cleaned as well.
I would also look for bad ground or loose connection anywhere in the fan circuit.
Rob