Alternator-Starter motor-battery wiring

[csmacg]

Hi,

I have just put the (refurbished at home) engine back in the van. I am in the process of re-wiring and replacing the wires that need it. While doing this I have been using the Haynes manual wiring diagrams, but they don't match what's in the van already. I have looked long and hard online about the best way to wire an alternator to get the greatest voltage with the least resistance and I have a question that I would be grateful to understand better:

I have a thick (30mm cross section I think) wire running from the battery to the starter solenoid (terminal 30). There was a new fit pair of 6mm wires connecting B+ top spade on alternator to the starter solenoid. In addition there is another pair of red 6mm wires running from the same B+ spade on the alternator to the Engine Compartment Junction Box. There is also a singe red 6mm running from the same terminal on the starter motor solenoid to the ECJB. Why do they all meet in the ECJB? Why not just link the alternator to the battery (via the starter motor solenoid terminal)?

With thanks,

Chris.

[bigherb]

VW wired the alternator two different ways. Alternator to starter solenoid and a cable from the starter solenoid to power the ECJB. or alternator to ECJB then ECJB to starter solenoid.
Looks like yours was the second system and someone has put additional cables from the alternator to the solenoid.

[CovKid]

If you read my WIKI on replacing those cables, I mention the ones that go to the black box:

https://club8090.co.uk/wiki/VW ... ain_cables" onclick="window.open(this.href);return false;

As you have figured out, you can snip those and just run single (thicker ideally) cable from alternator direct to starter - if the alternator connection allows you to do that..

Sounds like you have a similar setup to what I had.

I now have an excellent connection using good quality cable. The original thick cable from starter to battery is still underneath - I just cut away what could be seen at each end and ran new stuff through.

[csmacg]

Thank you - really useful. There is so much advice that appears to contradict itself. My corroded cables looked exactly like yours!

The alternator has male terminals for W (separate - not sure what this is for), D (indicator light, blue wire), and 2 x B+ (connected inside I believe).

[bigherb]

W terminal is a phase tap for working the rev counter if the alternator is fitted to Diesel engines.

[CovKid]

Fairly common if the vehicle's main cables haven't been touched since it was built. Originally I'd intended to just make good any terminals but the cable was dreadful no matter how far I cut back and previous attempts had merely made the cables shorter anyway. No way was any of it fit to take solder. The only thing to do was replace the lot and start again.

I do recommend the use of solder where you can and carefully placed shrink tubing as it keeps the air/water out - bit more involved but well worth the time and effort.

The biggest part of the job was securing a suitably sized blow torch for the ring connectors, getting a feel for how much insulation needs to be cut back, and avoiding solder running too far along the cable. One of those 'helping hands' rigs or at least a small vice is damned useful.

My corroded cables looked exactly like yours!