Club 80-90 Forums

Ok, I started a long drive yesterday & not long after I set off my battery warning light came on. I had a spare regulator so swapped them out but still the same.
I managed to get my destination very late last night with hardly any juice left in the battery so it's obviously not charging. For various reasons I won't go into I can't get to the van to properly test it with a multimeter until after Christmas. So, my question is.. apart from the obvious fault which is a knackered alternator, is there anything else I should check before I cough up for another one? Ta as usual in advance.

could well be the wire from alternator to the startermotor , which is known to go high resistance ,
but as you say the charge light is on id be checkikng the blue wire isnt damaged

defo blue wire, thats where I would check

heve a look at my struggle before you buy a new alternator

http://forum.club8090.co.uk/viewtopic.php?f=39&t=163707" onclick="window.open(this.href);return false;

crazyhorse wrote:defo blue wire, thats where I would check

heve a look at my struggle before you buy a new alternator

http://forum.club8090.co.uk/viewtopic.php?f=39&t=163707" onclick="window.open(this.href);return false;

That looked like a right palava.
Anyway, after reading up, what I can glean is that the blue wire goes to the split charge relay under the seat in the battery compartment?

captain Byrne wrote:

crazyhorse wrote:defo blue wire, thats where I would check

heve a look at my struggle before you buy a new alternator

http://forum.club8090.co.uk/viewtopic.php?f=39&t=163707" onclick="window.open(this.href);return false;

That looked like a right palava.
Anyway, after reading up, what I can glean is that the blue wire goes to the split charge relay under the seat in the battery compartment?

ha it was. To be honest Im still not sure what was going on... Check connections between alt and starter before you buy anything..

captain Byrne wrote: Anyway, after reading up, what I can glean is that the blue wire goes to the split charge relay under the seat in the battery compartment?

that is correct, HOWEVER, the blue wire is the alternator exciter wire , and is original to the vw loom, it is tapped into to trigger the splitcharge system and fridge in a camper conversion.
without it the alternator will spin, but not charge .

Mocki wrote:that is correct, HOWEVER, the blue wire is the alternator exciter wire , and is original to the vw loom, it is tapped into to trigger the splitcharge system and fridge in a camper conversion.
without it the alternator will spin, but not charge .

Ok, just to clarify. I need to check continuity of the blue wire from the alternator to the spilt charge relay, and also from the relay to the dash battery light?
I know the alternator isn't charging the battery so is there a simple test I can do on the alternator to check it?
Also, I guess if I checked the voltage on the D+ terminal, that should around 12V?

if you put a multimeter on the output ( big connection) on the alternator and there is no output , apply 12v to the blue wire connection ( small connector) the alternator out put should be 14v at engine idle.
if this is the case the alternator is working correctly and the blue wire is at fault .

this test can be done on the bench , alternator in the vice, spin it with a drill or rattle gun and apply 12v to exciter connection once its spinning you will feel the torque change and voltage output will show on meter.

Thanks Steve, will give that a go.

Ok, bit of an old thread this but I've only just got round to having a bash at fixing this.
Anyway, I've tested the blue wire at the alternator & I get 4v. When idling I get 12v at the main connector on the alternator and when I connect a 12v wire to the blue wire connector I still only get 12v when idling. I'm guessing the blue wire is ok & the alternator is shot?

I would be looking at https://www.brickwerks.co.uk/voltage-re ... 14-5v.html" onclick="window.open(this.href);return false;

Make sure before you spend any cash that you were taking those voltage readings using the alternator casing as neg connection for your meter , and not the body or battery . Or your readings may not reflect the true story , which could be a earth issue .....
Alternator or wiring?

Those voltages don't sound like they are accurate - I would expect to see some decimal points there rather than a straight 12v.

Thanks Steve. The first thing I did was replace the regulator so I've ruled that out.
The voltage was 11.8 - 11.9. Earthed on the alternator. The fault has been intermittent, but mostly not working rather than working.
I'm getting around 4 volts on the blue wire right up to the dash connector.

4v with reference to what ground point?

On the dash end I'm earthing on dashboard. At the alternator I'm earthing on the casing. Can't understand why I only get 11.9v when I'm putting 12V to the blue terminal. Surely that means the alternator is knackered?