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Old 19th September 2019, 11:25 AM
mannyo mannyo is offline
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Join Date: Jan 2012
Location: Blandford, Dorset
Posts: 1,974
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J126 is the part I replaced, but the replacement I got was a used one from a car of similar age.

It's quiet possible that the used one is also faulty, so I might go ahead and buy the new no OEM one from ebay.

J126 is what controls the fan speed, it has a number of inputs, and just two wires going out to the fan motor itself.

The fan is definitely running on solar power when the engine is running, you can see it spinning quiet happily by looking into the box with the pollen filter removed, ant it's speed varies based on the amount of sun.

There is 12V coming into the controller from the car side, and the voltage from the sunroof varies based on the amount sun.

It is possible of course that J255 is faulty, in that maybe the required signal is not getting to J126. I have no means of checking this as I do not know what the signal that controls the speed of the fan into the controller is meant to look like. J255 has component protection, so it's not easy to just swap a replacement in.
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Manny
2004 A4 1.8T Sport Cabriolet, 89K Miles
Past
2004 D3 A8 3.7 Quattro, Xenon, Bose, Blinds, Solar Sunroof, TV, ACC, phone and almost every option. 168K miles rising slowly
with retrofit AMI and DVB-T in place of Analogue
2003 Volvo S60 D5 SE Manual, 197K miles.
2001 D2 A8 3.7 QS, Bi-Xenon, Bose, Blinds, Electric Everything, retrofitted RNS-D, 191K Miles

Last edited by mannyo; 19th September 2019 at 11:42 AM.
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