Fuse 9 under the seat is 20A and controls "Front audio system amplifiers, front doors" according to the handbook.

It first blew a couple of weeks back. The door winders and fobs suddenly stopped working. I replaced it and it was OK for about a week. Now it repeatedly blows again and I have been unable to trace what is causing it. I fit a new fuse, turn the ignition on, and the window winders, locks and radio all work again. As soon as I start the engine, it blows. Is there anything else that runs through fuse 9?

My HEVAC central LCD panel is also currently off and I don't know if this is related. The switches light up ok but no display. I swapped the panel for another spare (but an early one) and it doesn't light up either. I swapped them back and tried unplugging relays under the bonnet related to HEVAC .... heater blowers, aircon clutch etc. Still blows.

Disconnected radio leads. Still blows. I have also added a few things to the wiring over the years ... a switch for the aircon fans (wired through a relay anyway) and a USB connection/Hella charging panel in the back. Disconnected all the leads. Still blows. Running low on 20A fuses, I fitted a 30A fuse. Still blows. Plugged in a diagnostic current measuring device that you plug into a fuse socket and it went off scale and blew the fuse in the device.

Turning the ignition on, everything seems fine. No short circuits. No blown fuses. Start the engine (diesel) and it blows with a pop. Any ideas?

According to the diagram in RAVE, fuse 9 only feeds the front door outstations and the door amps are fed from that. The supply splits inside the BeCM and then goes to the RH door from pin 2 of C1586 while the LH door is fed from pin 8 of C1291. The supplies go via connectors by the door jamb, a 6 way white connector. For the fuse to blow when the engine is started would mean that one of these two supplies is shorting with something that is grounded when the engine is running but I can't find anything suitable in close proximity.

Thanks.

Just come back in. I think I have found something, but haven't pin pointed the problem exactly as yet.

New fuse fitted, turn on ignition, tried moving the mirrors: passenger side ok, but when I try moving the drivers side, the fuse blows.
Door winders are ok.

Fuse 9 was pulling 0.3A with ignition on. Then goes off scale and blows 20A fuse in my fuse tester when the mirror is moved.

Door outstation? door wiring or connector? mirror switch? Will check further tomorrow.
How can starting the engine blow the fuse?

It will be something in the door/mirror - as the mirrors are told to move over a serial data connection. So if the window is working, door amplifier etc - but the fuse blows when the mirror is moved, then its either the mirror motor has a short in it, or the wiring between it and the outstation. Or a fault within the outstation itself that is on the mirror driving circuitry.

I'd unplug the mirror (pop the tweeter off and you'll see the plug), replace the fuse and try and move the mirror - obviously it won't move, but if it doesn't blow the fuse, the fault is likely within the mirror itself.

That makes perfect sense although it doesn't explain why the fuse blows when the engine is started????

I wonder if the car has memory seats?

IIRC the system should set the seats and mirrors to whatever is saved to Memory 1 if Key 1 is used (Memory 2 for Key 2 etc) when the car is started.

I guess it must put some current through the mirror to check if the position is correct before adjusting it if needed.

I had forgotten about that and yes it is a bit odd true...

I think the seats and door mirrors should only move if you unlock by pressing and holding the unlock button - and if RAVE is to be believed, that only works if the vehicle was superlocked before. I wonder though if it might try to move the mirrors a tiny bit to just move the potentiometers and get a reading from them at startup. Just a theory mind...I can't say I've paid that much attention to the mirrors, not that you'd hear them move with my lack of exhaust :)

It is the driver's side door mirror ! I unplugged it and the fuse doesn't blow when the engine is running. The car doesn't have memory seats.

I plugged the mirror back in to confirm it was the problem, fully expecting the fuse to blow again (I have had a box of 100 fuses delivered by Amazon) and there was a puff of smoke from the connector when I tried operating the mirror! I stopped at that point.

Clearly a short on one of the motors in the mirror I think. Next job is to swap it for a spare mirror I have got. It is 6 pin.

Are they permanently heated like some BMW door mirrors?

Good point, yes they are permanently heated and I wouldn't mind betting they are configured to only power up the heating element once the engine is running. Sounds like a short inside the mirror so it shorts out when either the heating element is powered up or the mirror tries to move.

Just found this. The wires have been trapped by the metal body of the mirror.

I can't remember ever having taken the mirror off myself. I have replaced the glass but that is about it.

I had the door and mirror resprayed by a crap body shop about 8 or 9 years ago when it was damaged when parked outside my house.
They must have been clumsy bolting it back on.

I think you've probably found the fault......

OK, just use electrical tape on it, don't be tempted to switch over the colour coded part with your spare wing mirror, it's a total PITA.... I did do it, but only because the colour coded cover of the fitted unit was badly cracked, and the replacement I got was not a heated unit ie wrong body connector. God knows how they assembled them in the factory - the wiring goes right through the centre of the pivot, with a heavy spring and massive starlock-clip in the tightest of spaces. It looks like they put that part of the wiring through the pivot from the connector side before splicing it with the wiring for the mirror servo and putting heat shrink tubing over it

Thanks, but I have now repaired the wiring. I cut out sections of the two damaged wires, soldered in new sections and protected it using heat shrink tubing. I have moved on to my Hevac display now.