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Old 07-30-2019, 05:32 PM
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wpoll wpoll is offline
Join Date: Sep 2015
Location: South Island, New Zealand
Posts: 3,554
wpoll will become famous soon enough
Originally Posted by wpoll View Post
The diagram certainly isn't correct, from a circuit path perspective - and the actual circuit diagrams (as shown in the TIS documents) don't seem to match what folk are finding in their cars either. And there does seem to be a bit of variation - e.g. my 3.0d has only a single cable at the jump terminal, running down to the starter motor (I think - I'll check more closely when I service it next week)., so no "hot jump terminal" for me.

Such fun... it's like our very own "Tower of Babel".
So, I said I would look into this (at least on my own car) and confirm what was actually going on and lo and behold, what I had always assumed to be a single-ended terminal - the B+ jumper post - is ACTUALLY a bulkhead pass-through!!

Peeling back the scuttle below the windscreen, I spotted the large battery lead coming up from the back of the car and connecting to the back of the B+ jumper post, via a large bulkhead-pass-though connection.

From there, a large lead runs down to the starter solenoid and then another runs from the starter solenoid to the alternator.

All this can be seen in the following parts diagram, with #6 being the passthrough terminal at the bulkhead. #9 Is presumably the lead to the starter and alternator on the M62/N62 cars (not used on M54/M57 cars): -

So what is in my car doesn't match (exactly) the wiring diagram I posted earlier nor does it match the circuit diagrams in the TIS...

How YOUR car is actually wired may depend on where the starter is located - on my M57TU the starter is directly behind the alternator (left side of engine block) - same as the M54 but on the opposite side for the M62/N62engines, so the diagram above may be closer to what is in the V8 cars.

The important aspect to note is that, like many members have now discovered and in contradiction of most TIS wiring diagrams, the B+ jumper post is a VERY important connection point in the circuit from the battery to the starter and alternator - apparently in all E53 model variants.

Keep it tight and clean, boys and girls...
2005 BMW X5 3.0d (b 02/05)
2001 BMW F650GS Dakar (b 06/01)
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