Hi, fitted new alternator to my 2004 4.4 v8 petrol today. Voltage reading around 14v to 14.2v when engine on which is ok.

But v odd that battery light doesn’t come on when I turn ignition on. It was working before as it was on when old alternator failing.

The wiring diagram shows only 3 wires to alt. The big red wire to started and 2 in the push in plug.

The Plug is in and big wire bolted in.

Does the bulb fail ever? Could I have broken something during dismantling?

No faults recorded on IIDTool reading.

Any thoughts?

Cheers,

Sten.

So, if I take the plug out of the alternator and take a spare bit of wire from pin 2 of the plug to an earth point the battery light comes on. So the led is functioning.

I’ve taken the alternator out and arranged to take it back for an exchange unit tomorrow but before I did I checked continuity between the alternator pins and alternator body. There is continuity.

Confused now as I can’t believe the alternator body isn’t earthed when bolted to engine. So is it just a duff alternator which appears to be in continuity when passively tested but balls up when voltage is applied?

Have you done anything to the battery recently?

Charged it overnight as it was a bit low. Also cleaned the battery Earth strap to body connector.

Worth checking the battery terminals. As you say the light should be on when you switch the ignition on.

Yes, they look clean. Battery less than 6 months old. Still can’t understand why light works if I bypass alternator but not if plugged in.

It's looks as though it is either the plug connection or the alternator.

Duff alternator. Got a replacement today and all ok. Really frustrating I needed to drain and refill the coolant but at least it’s all working now.

I remember them being VERY expensive too back in the day!

Glad you got it sorted sir, if a little frustrating!