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'85 4000q 3B Swap - need wiring help :|

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 Post subject: '85 4000q 3B Swap - need wiring help :|
PostPosted: Mon Apr 20, 2020 7:14 pm 
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Looking for some advice on wiring a 3B into an '85 4000 Quattro.
I removed the wiring harness that came from the Motronic ECU behind the glove box - and I see there were only 2 plugs that went from the Motronic ECU to the fuse block on the driver side (bottom right of attached picture). When looking at the 3B harness there are tons of connectors on the interior side of the harness. I've test fit the engine bay side of the harness - so I'm pretty sure I'm looking at the right stuff.
Do these need to be integrated into the fuse block or are they not needed because of the OEM 4000 driver side harness?

I've been reading through several other 3B swap threads trying to find info on wiring and find bits and pieces, but nothing I've found is a step by step guide for dummies like me :wink:
I do have Bentley manuals for the 4000 and '91 200 (3B) - but people seem to say often that the 3B swap wiring is pretty easy :P

This thread mentions which wires I need to customize, which will be no problem - but I am unsure about the rest of this mess of connectors.
https://www.motorgeek.com/viewtopic.php ... &start=375" onclick="window.open(this.href);return false;

Thanks!

Some background - I started this swap a while ago - never done an engine swap before but have countless hours of DIY wrenching on various other cars.
I rebuilt the engine and turbo and it is currently installed into the 4000 - and obviously needs most of the wiring to be completed.
Current plans are to use all stock parts for the 3B.
Stock turbo, ECU, wiring, etc. My end goal is a 'simple' swap, looking as much as possible like it's supposed to be there :P we'll see how that turns out.


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 Post subject: Re: '85 4000q 3B Swap - need wiring help :|
PostPosted: Sat Apr 25, 2020 5:04 pm 
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https://www.audiworld.com/forums/audi-original-s-cars-25/audi-s2-3b-original-wiring-harness-illustration-2932707/

This, and other UrS4Boy posts will be helpful. Note the fuse box representation at the top of the schematic (the large gray bar with the fuel pump relay inside) and the connection points exiting the fuse box - H87F, O, 87a, BS, B15, 30, M30ac. These numbers either refer to a whole connector, or a single wire within a connector. Some connectors, like O and 30, plug right in, others you'll have to de-pin the existing 4k connector and put the 3B wire in its place.

Connecting those 7 wires gives you a fully functional motor. If you're feeling fancy you connect the tachometer too for a total of 8 wires.

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87 4k, 90 f350, 91 v8, 93 v8, 04 s4


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