Alternator not charging - Fixed

My battery warning light has stopped working, resulting in the alternator not switching on, so no charge and fully charged battery dies in 45mns of driving.
Any tips on how to troubleshoot? Original VW dash and wiring, Subaru EJ25 motor.
I did do a little work on my dash then noticed the light not coming on when switching ignition, so must’ve disturbed something.
Is there a fuse in that circuit? Location?

Thanks in advance,

Those blue foils are very brittle.

I gave up on mine a long time ago and bought one of those South African hard wired kits.

They are easy to install and dont fail.

Yea I think I might have to take the plunge and order that one…

Anyone with any tips on testing the battery (charge) warning light circuit?

Also another question, with a 200AH leisure battery and DCDC charger fitted, has anyone upgraded their EJ25 alternator to a higher output, and if so, with what?
Any alternators from bigger Subi engines fit?

Thanks in advance,

Thoroughly agree. The kits are great and easy to install. No more foil to worry about. Peter

Hi Gaetan,

This what I was advised is a way to test the circuit:
You’d need to do an amp load test to see if it is putting out a “full” charge. The alt warning light is a unique circuit. Key on engine off, the warning light has 12 volts on it and is grounded through the Alternator. When you start the engine, this load excites the alternator into charging. 12 volts is fed back up to the light and cancels the 12 volts on the other side of the light, causing the light to go out. A glowing light indicates a voltage difference on both sides of the bulb. Resistance in the wiring and connections can cause this. You can isolate the wiring, by using a test light. The blue wire on the alternator is the wire to the warning light. Most vehicles have a t1 connector. You can unplug the wire and probe it with a test light connected to a positive connection. The test light should light. Start the engine and the test light should go out completely. If not, you need to look into the Alternator. Most have regulator as part of the brush holder. The brush assembly can be purchased separately. Since you are seeing an increase in voltage, you should be ok to drive home. Drive in the daylight and don’t use any extra electrical loads. Keep the stereo off. Once you get home you can do some troubleshooting.

This little gadget from GoWesty may also help:

Hope it works out.

Not sure on higher output alternators but I am sure there is something out there…Maybe get on a Subaru Outback forum - maybe they have ideas on bigger alternators?



Thanks for all the info Scott. I’ve taken the alternator out and will have it tested first as that’s easy and quick.
Either the diodes went as my leisure battery died and it kept trying to charge, or something’s gone funny in the instrument cluster with the battery light.
That will be my next lot of testing - I need to fond a way to a) test the resistor/LED in the cluster, and b) make sure the battery light circuit is good up to the cluster multi connector.
I will get there!

Disconnect the D+ or DF (the wire to the light) at the alternator and earth it. Turn ignition on and the light should be on. This will test the light, foil and wiring.

Found the fault at last: in the multi connector that attaches to the dashboard unit, the 4th connector (11) spring pins had gotten caught and bent down all the way :frowning:
Luckily these older plastic connectors can be popped open by inserting a tiny screwdriver in 3 places, having done that I was able to pull out the blue wire and carefully reshape the spring pins so they make a nice solid connection to the blue foil again - et voilà - charging light straight back on with ignition and off with alternator doing its job again.

Simple fix in the end but lucky find while inspecting the connector closely!

Thanks for all the suggestions guys.

Nearly all of the dash foil problems are like this, Caused by ham fisted mechanics. The actual design of the foil is OK.

Excellent work Gaetan.

Finding of these problems is often much more painful than the actual repair.

I know. It was a relief when I clocked it!
What I don’t understand is how it got bent in when it’s a perfectly flat surface mating against the pins!?

With you there Gaetan. I have one of the pins from the temp sender wire that is very dodgy. One part of the little connector is broken and it can sometimes not connect. The previous owner even ran another wire from the sender to the instrument panel connector when all along it was the connector I reckon. Anyway I have replaced the foil as it was a bit wrecked in places. Especially where the small light bulbs go in. Used the South African kit. Works a treat.