Thank you ALL so much for replying.
I think this started with me checking the DTC codes when the blower packed up. It was throwing 419 so I checked my Haynes which indicated 'Faulty diagnostic signal from blower fan power stage' and iirc 418 is 'No control signal to blower fan power stage'. After some web searching I discovered it was the resistor pack which apparantly, I read somewhere, is a basic chopper circuit.
I understand there is constant 12v on the thick blue wire and the power stage (resistor) varies the ground. Iirc a oscilloscope is needed to measure the digital signal from the head unit which is way out of my league. I have read many posts where the mosfet has been replaced successfully and some posts with equal failures. Since there is 12v permanently hot all the time (key out) I am scared to mess around replacing mosfets for fear of a fire.
I called Doves (Volvo dealership, Croydon) and was told the part number is now discontinued and my best bet was to search a salvage yard. Most scrap dealers around my end have closed (price of land) and the few I went to have no 850's.
I travel to Dunstable a few times a year.
Is Frf in Swansea a main dealer?
I am swaying towards buying a second hand unit on ebay and somehow making it fit.....thanks Rolling Thunder I was thinking the parts are similar with the only difference being lhd and rhd but happy to take a punt at £30.
Sadly, I only ever focus on this problem when the cold days set in.
Thanks again
Andre
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