Battery Not Charging - Mk2 1.8T

Ive been driving the MK2 around today, and found out that the battery had completely gone flat.

Its definitely not chaging, as the battery is fine.

Im sure there is a wiring fault somewhere.

Here is a quick diagram of how everything is wired in atm -



Any ideas anyone ?

Cheers

 

The large red wire from alternator should go to either outer starter solenoid positive connection or battery positive, as per drawing above.
But the little blue wire should connect from the two pin connector on the alternator to the blue wire connection around the battery area that then goes the the dash warning light. Not the battery. You need the blue wire connected as it is the warning light and the exciter connection to make the alternator charge.

 

Cheers for getting back Dan.

This is where the two pin plug is connected to -



Im guessing thats where im going wrong as my battery light is constantly on.

Where abouts is this other blue wire which turns off the warning light and starts the exciter ?

 

There should be a small single blue wire that feeds into the main engine bay loom back to the fusebox. I think that is actually the one you are holding in the pic if it has the female end inside. If not it is the other one hanging down by the looks of it.
You only need this small blue wire connected to the D+ connection on the alternator which is one of the terminals in the small twin pin connector of the alternator.

The other pin of the small twin plug connector is the W terminal and is sometimes used for a rev counter signal on diesel models.

 

Just been outside to have a look Dan.

Basically i had a two pin plug plugged into the connector, then wired to the blue wire.

As said above, one of the terminals in the 2 pin plug D+, only needs to be wired in.

So ive run a wire from the D+ terminal to the blue wire, and the battery light is still on ?

Im sure that the blue wire is fine, as when i disconnect it, the battery lights stays off, so im guessing its not shorting out anywhere.

Am i still doing anything wrong ?

 

Is there any way of checking if the alternator is running ok ?

 

It could be the alternator is not charging. It could be if it has been run for extensive time without being connected correctly that the regulator / diode pack may not like it.
In basic terms the blue wire gives a positive feed to the alternator which is earthed when the engine is not running, this allows the dash warning light to be lit. However when the engine starts this 12v feed is the exciter wire to the alternator control regulator assembly, and the blue wire then loses it's earth and the charge warning light goes out when the system is operating as it should.

Have you got a pic of the alternator? I cannot remember if your engine is the early type or not. If it's early I probably have an alternator up here that would do.

 

Cheers for the info dan

Here is the alternator ive got -





I bought it off the guy who sold the engine loom to me.

My engine colde is AGU. It was all from a Audi A3 1.8T - AGU. So im guessing early type i think ?

 

This is exactly what mine looks like close up, as the pictures i posted were not as clear.

The D+ has been labeled which is good, so will double check that tomorrow.

Just hoping the alternator is not faulty !

 

Right then, i wired everything in today.

Found a two pin plug and used that to plug into the D+ socket. I removed the wire which connects to the W.

Wired that up to the blue exciter wire, and still no joy ? The battery just ran flat!

So whats my options now ?

Replacement alternator maybe ?

 

So does the charge warning light on the dash stay off with the ignition off, illuminate when the ignition is switched on, and does it stay on when the engine is running?
If the above is true then it does sound like the alternator is the problem.
However, as you have presumably been playing around with the wiring during the conversion it may just be that something has been altered circuit wise and is causing the problem.

 

Have you checked the battery voltage with a multimeter. Should be around 14v with the engine running.

Could be the voltage regulator if it isn't charging.

 

The light is constantly on when the engine is running Dan.

When the exciter wire is disconnected near the battery when the engine is running, the light on the dash goes off completely, so i think all is well with that.

Must be the alternator. It looks like its in good condition but i suppose anything can become faulty.

I'll have to borrow one and see what voltage its pushing out.

 

That was an old picture when i was testing the starter motor out.

This is where i may be going wrong then ?

Ive got the thin blue wire with the ring terminal going to the small stud ( like the 8v setup), and an extra wire from D+ spliced into the blue one.

I suppose this is where im going wrong ? Shall i remove it from the small stud ?

 

I suspect so. Almost facepalm worthy in fact.

What stud?

You only need, one small blue wire from D+ to the thin blue wire in the main loom, and one heavier red wire from the M8 stud with 13mm nut connection on the alternator which goes to the starter solenoid (battery side, not the lower one that goes to the starter motor windings when the solenoid is activated during cranking).

 

Cheers for getting back Dan

The small one, next to the labelled lower bracket in this pic -

Just been around the lock up. Wired it all up as above, and still the same thing!

The light stays on and its not charging!

When i disconnect the D+ the light on the dash goes out completely, so im guessing this points to a dodgy alternator ?

 

Gonna get some pictures up in a while. Im just on my way round to the Mk2 hoping to get to the bottom of this!!

 

This is how its wired in -

* Starter Motor Wiring.





* An extra wire, with a 2 pin plug, wired into the blue exciter wire.



* 2 pin plug which connects to D+





* The alternator -



So does everything look ok