You could also diagnose it with a volt meter. If you put the meter across the motor first, that'll rule in/out a motor problem. Running normally, I'd expect to see a voltage that changes with fan speed. When the fault occurs (ie fan not running when it should be), 12 volts would suggest a motor fault and 0 volts a controller/power fault.
If the first test suggest a controller/power fault, attach the meter's ground to a permanent ground connection (leaving the positive wire on the motor's supply connection). Running normally, you should have 12 volts. When the fault occurs if you still have 12 volts the problem is with the 'hedgehog' (or associated connections), if you have 0 volts, the fault it with the supply.
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Mark
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2002 FE S8 Ebony Black Pearl
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Cars Owned:
The Tesla Era: 2020 Model S Performance Ludicrous+ (present)
(Black, with all black premium interior and carbon fibre décor, 21" sonic carbon twin turbine wheels and FSD capability)
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The Citroen Era: '84 BX 1.6 RS --> '89 BX 1.9 DTR Turbo --> '94 XM 2.0L Turbo --> '96 XM 2.0L Turbo Exclusive --> '00 Xantia Activa 2.0L Turbo
The Banger Era: '76 1.2L Lada VAZ-2101 (Ruski Fiat 124) --> '80 1.7L Morris Ital HL, finished in Ermine White and Rust
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