VW Electrics main cables

Introduction - Good Connections

(Under construction)

Intro by Covkid:

Good connections and good cable are essential for effective charging and starting. However, after 30 years work, the main heavy-guage cables that go from alternator to starter and battery can be subject to deterioration. You need at least 4 metres of new cable do this job - suggested types at the end.

The thickest cable by far is the one between the battery and starter and if you drive a T25 with your main battery behind the drivers seat, you'll realise that its quite a distance between the two. The alternator cable isn't quite as chunky but for this upgrade I replaced both of these cables with the same 25mm fine strand cable. Its just about bendable at that thickness.

Cable corrosion

The photo below shows the terrible (although not untypical) state of a cable at the rear of an alternator. This is acid corrosion which can also cause the insulation to crack and break away leaving bare copper wire. Most alternator connections actually terminate in a plug rather than like this and therefore the state of them can easily be missed. The copper within either starter or alternator cable can become brittle and corroded, no matter how far you cut back, and potentially create resistance - reducing the alternator's ability to charge and the starter's ability to turn the engine over. The stands can break too, further reducing the capacity of the cable.

Generally, when things have become this bad, the only thing you can do is replace the cables completely and solder new connectors as and where required. You can crimp (if you have access to oversized crimps) but soldering makes for a more reliable connection and helps seal the cable.

This particular engine a 1.9DG and wiring layouts do vary. It also uses a golf alternator rather than a stock one so only has a single nut which holds the main cable. You will need to decide how best to replace corroded cables in your setup.

Replacing cables

I started by removing the old corroded cable on the alternator (above photo) which was not one, but two cables, twisted around the post and clamped between two washers (not by me!!). This cable doesn't, as you might expect, go directly to the starter terminal as it did on so many v-dubs but goes to a post connection inside the black junction box in the engine bay on the left (see photo below).

I puzzled over this for a while, checking either end to figure out why it was wired this way, and to be honest it still makes no sense unless it something to do with assembly process at the factory. After all, another seperate red wire on that post in the junction box also goes to the starter motor main connector so effectively all went to the starter motor connection anyway!

I gave up musing this one, decided to snip alternator cable in that box completely (you can see ends in photo) and just run the new alternator cable straight to the starter terminal with another soldered ring connector. I figured it was easier to just keep it simple. I couldn't see any sense in running a big chunky cable to that junction box at all. Seemed ridiculous.

The vehicle is a 1.9DG and wiring layouts do vary.