[rescue] HP 9000 A180c fan replacement

[Meelis Roos]

One of the three front fans of my HP A180c started to get noisy. It still
worked but was loud.

So I ordered a new one with same size and roughly the same power draw
(but not exactly). It has same 3-pin connector but with different wire
color order (red and black swapped, yellow in place). The new fan spins
but the firmware detects fan failure and shuts down.

Now, how do I check what it expects? Maybe the yellow wire is for RPM
like on PC-s and the RPM reading is just out of range? Or maybe it just
takes "fan good" like in some Alphas so I would need to wire the third pin
to either plus or gound?

I do not have a oscilloscope to check the frequency, just a simple
voltmeter/ampermeter. What would be the best way to find out the expectations?

-- 
Meelis Roos <mroos at linux.ee>