[Techtoolslist] 9010 fan question

[Tony Jones]

My 9010 started making a weird pulsing noise which I tracked down to
the fan.  Like it was trying to start but couldn't.

I've never given the fan any thought before,  does it run all the time?

It's just two wires off the motherboard (which weren't pulsing per my
scope) but these go to some kind of fan sending unit which feeds 4
wires to the physical fan.  Is this some kind of temperature control?
The fan blades didn't spin easily, quite a bit of resistance so I was
assuming the fan itself was the problem rather than the sending unit.

I have the model# specs for the fan so I'll look for a replacement but
that might be challenging, replacing just the fan part and connecting
to the existing grey sending unit may be another option. I couldn't
find any previous mention of this in the archives,  curious if anyone
has been here before?

Thanks!

Tony