Starter motor wiring and leisure battery

[aisha]

I've been trying to reinstate the wiring in my Westfalia to what it ought to be (as detailed in this useful article):
https://club8090.co.uk/wiki/Ca ... y_charging" onclick="window.open(this.href);return false;

I found that the "earth" side of the charging relay was dead - the earth side isn't really an earth, it is a feed from the ignition / starter wire - it means that the leisure battery, fridge and main battery are all isolated during cranking.

The ignition/starter wire had been cut as the relay mod was performed, where a relay was put in the engine compartment, the same wire (red/black) is now a trigger wire to the relay going to the starter.
When I tried to splice the charging relay trigger wire back into this circuit it started cranking the engine (presumably as 12v was coming through the switch - which would trigger the relay, and send that voltage back to the starter relay)
When I tried to bypass the relay and use the red/black wire connected directly to the starter motor it didn't trigger the starter motor (presumably not enough current?)

So I'm planning to run a new wire between the ignition and the starter - thus reinstating the original wiring.

BUT I can't see what stops the 12v coming from the alternator light from triggering the starter motor? Is it a case of amerage? ie there is 12v but a large amount of current going through the ignition/starter cable when the key is turned, but only a small amount of current coming through to light the alternator


IN SHORT!
In this diagram:
https://club8090.co.uk/wiki/Ca ... y_charging" onclick="window.open(this.href);return false;
Why doesn't the alternator light wire going into the charge relay trigger the starter motor?
As when i had a relay switching the starter motor it did crank the starter...

( I could ground that side of the charge relay but a previous owner has performed enough bodges that I'm sick of them)

[colinthefox]

In this diagram:
https://club8090.co.uk/wiki/Ca" onclick="window.open(this.href);return false; ... y_charging
Why doesn't the alternator light wire going into the charge relay trigger the starter motor?
As when i had a relay switching the starter motor it did crank the starter...

You're quite right that there's not enough current (amperage) flowing in the alternator light circuit to trigger the starter, but there might indeed be enough to trip a small relay.

It seems that the starter relay was rigged up as a work around for the starter not getting enough current to work, and this is the problem you need to solve. Your wiring (on the other thread)shows evidence of a bad connection (the frayed connection on the fat red wire at the positive terminal on the battery) which has overheated and melted back the insulation. This might be the kind of place to start looking to cure that problem, by soldering on some new lugs perhaps. Crimped connections are OK but the wire there is already oxidised, and won't make a good connection, and would burn again. When this happens I use "Everflux" which is what plumbers use to solder dirty copper pipes, and which will blast through all that red oxide.

Another place to look might be the ignition switch, which might be burning out.

[colinthefox]

OK. Just had another look, and the bad joint I mentioned above is one of the alternator wires, so not that one..........but it needs repair anyway. The two wires underneath look equally suspect though! Badly crimped and frayed.

[aisha]

Ok - thanks for that. I've bought some 17A wire to bypass the old red/black from ignition to starter - hopefully that will carry enough current to negate the need for the starter relay, and fix my leisure battery charging problem... but I will also need to fix the cabling from the alternator to the battery. Never heard of everflux, was going to cut them back to ascertain health, and if still no joy just replace them. And come to think of it, they might (add to) a difference in voltage between the D+ and B+ output causing the alternator light to come on...

It was mentioned that the ignition could be on the way out also... At least I'll have a few things to keep me busy!

[California Dreamin]

I've not looked at the diagram so forgive me if I contradict what is there. As far as I am aware, there is no connection between the small blue 'exciter' / ignition LED feed on the back of the alternator and the starter circuit.

The switching feed is simply a piggy back off that blue exciter feed on the back of the alternator....it should in no way back feed to the starter solenoid.

Martin
'

[aisha]

Finally got this working as intended last night!
I ended up keeping the starter solenoid relay, and feeding the signal from that back to the charging relay.
It seems that either the ignition switch is on the way out, or the wiring has decomposed to an unhealthy amount - either way, the starter solenoid relay is necessary for the time being...

The charging relay now switches after engine has started. Will take it for a run later and see what voltage the battery is seeing.

Now that is solved I can move onto fixing the fridge and wiring the radio and interior lights to the leisure battery!