Cabin vent fan works strange

[MiA995]

After a "major service" or "big service" on the Citroen C4 Picasso 1.6 Hdi 80 KW, automatic air conditioning, two-zone, manufactured in 2010, we have a problem with the operation of the internal fan. Sometimes it won't work at all, sometimes it starts working and then stops, and sometimes it works perfectly. Fan removed, cleaned and lubricated, connectors cleaned physically and with contact spray, when turned by hand, there is no blockage, but it turns with slight resistance. When connected to 12V it works and when there is a resistor (6441 CE) then it works and stops.
I don't have the possibility to test the resistor (or rather, I don't know how), and unlike the one from the previous Xantia 1.2 TD vehicle, this one doesn't have the possibility to replace the transistor on the board because it is filled with some black mass.
Any advice is welcome.

[GiveMeABreak]

The most common failures are the resistors. If it's playing up it probably just needs replacing. Make sure you get a decent branded one.

[MiA995]

Thanks Marc, appreciate your help