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Rude View Drop Down
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    Posted: 09-May-2012 at 09:25
I have a situation, when London had all that snow years ago, so i was told, the car didn't start after. It was towed to a magic place in order for them to revive it.they couldn't fix the fault but did perform a spell and got it running. They charged the fella £500and gave it back to him. All he had to do was this: remove fuse 21 (interior circuit), start the car, replace fuse 21, use the car......and this is the good bit.... Everytime he wanted to shut it off, open the bonnet and remove fuse 21 or it runs on. This is aggro for me so i had a temporary solution to wire the switch below the radio in line to fuse 21's circuit. This works great. The thing is and always has been, whilst the motor is running with 21 removed or off in this case, the unit above the glove box screams in pain! I can see the engine fuse box has been infiltrated and i suspect these mechanical marvals have robbod power to the ign circuit from fuse 21'and there it some kind of war going on as rarely the car remembers how it should be and stutters until fuse 21 is isolated and the car is restarted. I think melting snow and water ingress is to blame. So assuming they have destroyed the internals of the engine Bay fuse box, can i swap it over with another unit? I dont mind running it like this, but its not what the German masterminds intended in their design and i fear i am going to see further component destruction. I would be interested to hear similar accounts and find out just what's gone on here. Sorry for my basic knowledge but im new to BMW, some say i jump in the deep end most of the time, i like to think its setting new challenges.....ta
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Howard Quote  Post ReplyReply Direct Link To This Post Posted: 09-May-2012 at 21:46
Depends on what is wrong at the other end of Fuse 21. Its no good changing the unit until you find what is happening there, or you could find that the same thing happend when you change it. According to my workshop manual wiring diagram, that fuse serves interior lights, radio, glove box, flashlight, onboard computer, radio, memory and instruments.
How it starts with no power to any of those I don't know. Should have a red/green wire and be 7.5 amps.
However, if you just need to change the unit, the instructions are as afollows:
Take off the cover, pull out all relays and fuses, unscrew bolts, lift carrier, disconnect all wires.
To replace it, reconnect according to the wiring diagram and do the rest in reverse.
 Do you know which unit is grumbling above the glove locker?
1963 700 LS
1988 635 CSi
1990 M635 CSi no longer!
2001 E38 728i Individual


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rude Quote  Post ReplyReply Direct Link To This Post Posted: 09-May-2012 at 22:23
That is a good point, and i can't see any other circuits that have been hacked into. I've removed clumps of cell phone cable, something else and the remains of the BMW alarm which had most of it missing anyway.  It is the red and Green cable, I remember it well as I searched for it by torchlight breaking my back on the seats as I wedged my head in the footwells crevices. The unit is directly above the glovebox, bolted to the crossmember, black plastic box with white connection, ecu for something and I think there's only the injection left =D, I did see it on the wiring diagrams, its escaped my memory of its purpose but it has a high pitch whistle with 21 knocked out. I didn't know how it started either seeing the mass of cable under there. I also grabbed a permanent live from somewhere else for the radio, do you know how annoying it is resetting the radio 6 times a day?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Howard Quote  Post ReplyReply Direct Link To This Post Posted: 10-May-2012 at 11:10
The BMW missing alarm is the likely culprit. When these things stop working people often just pull them out in the hope that the car will still run. Unfortunately the alarm systems have a circuit that breaks the ignition circuit when the alarm is set, and reconnects it when the alarm is off. When removing the alarm system, you have to ensure that this break in the line is reconnected. Your temporary podge fixes this but not properly, which is why you are having problems. You need a friendly auto electrician with knowledge of the BMW alarm to sort it out, or a wiring diagram of the alarm circuit. Unfortunately I don't have one.
1963 700 LS
1988 635 CSi
1990 M635 CSi no longer!
2001 E38 728i Individual


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rude Quote  Post ReplyReply Direct Link To This Post Posted: 10-May-2012 at 21:35
That makes sense, i found the alarm ecu thrown in the boot with a bunch of loom and other parts, so (excuse the pun) alarm bells started ringing.... I do have the complete wiring diagram, unfortunately downloaded onto my phone so i'll scroll for 2 hours and i should find it.... then I can have a see at this wiring. Thanks for throwing some more angles on this curious issue Wink
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