Mk5 Banana 2.5 Alternator.

[rob_887]

Changed the alternator the other day. Now its not working

B+ has the main battery feed
D+ has a wire what i think is the (turning on wire) (it gets 12V as soon as the ignition comes on (even before engine comes on so may have been bodged in its life)
W (think its the rev counter but i dont have one so we will count this one out)


Well the D+ has power going to it when engine is on of 12V
But the B+ still only reading 12V.
So i'm guessing the alternator is a rubbish one.
BUT I need some one to explain the battery light on the dials how does that know when the alternator is dead. as mine is off all the time even with just ignition (when all the oil lights and them are ment to come on to show you if bulbs work ECT)

[MinorMatt]

Sounds like your bulb is blown which will mean the alternator never gets the "signal" to charge

[rob_887]

Sounds like your bulb is blown which will mean the alternator never gets the "signal" to charge

But it is getting the signal as D+ gets 12v when the ignition comes on ?? Correct???

[Altransit]

When you turn on the ignition 12v gets fed to one side of the lamp on the dash, and it lights up.
When you start and rev the engine 12v is sent to the other side of the bulb from the alternator, thus putting out the bulb ............... unless the alt is not putting out 12v

If the bulb is not working, then the alternator won't charge at all, even if it's good

[rob_887]

When you turn on the ignition 12v gets fed to one side of the lamp on the dash, and it lights up.
When you start and rev the engine 12v is sent to the other side of the bulb from the alternator, thus putting out the bulb ............... unless the alt is not putting out 12v

If the bulb is not working, then the alternator won't charge at all, even if it's good

I did take a wire from the battery + to the D+ (excite termanal) not sure if this is what your ment to do as i know nothing about alternators.
and it still didnt jump up in voltage. still was only 12v



So if i take the D+ off the alternator put it on earth the battery light should show up.

[rob_887]

So i'm guessing what i should do is.


Connect the (Excite feed) to the Earth of the battery to make sure the bulb lights up.?


I've already put 12v+ to the (excite feed) of the battery and the battery didnt up in voltage at all so i'm guessing the alternator is still dead?

[Altransit]

You need to investigate why the bulb isn't working correctly and connect the wires as they should be to make the alternator work

[rob_887]

You need to investigate why the bulb isn't working correctly and connect the wires as they should be to make the alternator work

O right. So how come connecting a 12v+ to the D+ wont test the alternator i'm confused.??

Alternator light will be a easy problem i just wana get this alternator back and get another if its not working
cheers

[Altransit]

O right. So how come connecting a 12v+ to the D+ wont test the alternator i'm confused.??

Me too, but I do know that the warning light bulb is a critical part of the charging circuit
Maybe someone a bit cleverer than me will come along and explain the magic of it to us