<<I unplugged sensor at thermostat housing again, and this time passenger side fan did not spin, until i gave it a spin. Hmmm....
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That side has motor wear, most likely brushes are getting down. Specialy if it spins free by hand,, if not , the bearings/shaft are worn.

I've been searching for an answer to similar problem myself, to no avail. So I'm anxious to see your outcome. I had a fan stop working. Called a local MB shop where they recommended a few sharp taps with a screwdriver handle. Apparenlty knocks a little dust off the brushes. Bought me a little time.

Anyway, I've been running hot in the warm weather for a few years now. I plan to keep on driving this car indefinitely, so I want to keep it operating at its potential. Lots of posts about resistors, relays, yellow coolant, clogged radiators, bad thermostats, temperature sensors, fan clutches, et al, ad nauseum.

Please, solve your problem and solve my problem. Thanks.