PASSAT Onboard Supply control unit Fuse 41 Keeps Blowing! No start

Hi I’ve just joined the forum and have got two Vws a MK6 and a b7 PASSAT.

I’ve been having major trouble with the b7 PASSAT.

So as per title the onboard supply control unit (j519) blows as soon as I turn the key to on position.

So the day before the car started and ran fine except for the fans not working. The following day I went to inspect the fan connector which was split and soldered a new wire however as soon as I connected the fan up the car cranked but didn’t start. It was like it had no fuel pump power. (Fans still not working at this point).

From here I unhooked the battery looked at fuses/relays and all seemed ok however connecting the battery showed the depress clutch switch and no start and a blowing of the fuse.

I’ve disconnected the fan wire to eliminate the possibility of a short there and have looked around that area for other possible shorts but none can be found.

I’ve had it scanned with someone’s VCDS and there is no comms with any modules/ecu and I get a open or short to positive on the clutch switch and that’s about it. I disconnected the clutch switch but still the same

The car then does not recognise clutch so it just shows depress clutch and won’t go any further. The heater/climate control/hvac also does not work or light up and all other electrics seem to work.

I can’t look the wiring up until Monday, have you disconnected the brake pedal sensor.

Thanks for the input Crasher.

All that faffing and it turns out it was the cigarette lighter so I’ve disconnected it however need to figure out why it’s shorting there. There’s no fuse blow now and ecu is back on and car cranks but no start however got the VCDS scanner man out and error we get now is “Fuel Pump Relay control circuit- short to ground”


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I would need to look at the current flow diagram