I don't want to shed any doubt on hoonks reply, but just in case the problem isn't solved:
I don't think the fan speed is governed by a resistor, but rather by a transistor (possibly
a darlington couple: one high gain, one high current, together both), the Fan Control Module.
What can happen is that, if the cabin filter is clogged, the fan will draw a very high current
to obtain a decent air flow. This current flows through the FCM which gets hot. It is cooled
by the air from the fan, but that doesn't work as it should be because the air can't flow since
the filter is clogged. The result is that the FCM burns/fails.
It is a known problem that the FCM can fail if the cabin filter hasn't been replaced for a long time.
I can't say that this is what happens in your car, it is merely a possibility.
The FCM works on the car's supply voltage, 12VDC. At the connector is a direct (fan can blow if
car is shut-down) 12V connection. If I am not mistaken, the fuse is 30A. The FCM will probably
fail to open circuit before the fuse blows.
Of course this is just guesswork, it is certainly possible that the FCM you received was a bad one,
although it did work for a short while.
Willy
144 GL (1974)--->244 GL (1982)--->940 GLE 2.3i (1992)--->XC70 2.5T (2004)--->XC90 T5 (2018)
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