Technical Alternator issues

[Rollcage]

I bought a 2007 1.2 a couple of months ago as a cheap run around.

It seems to have a charging issue, in that the alternator isn't outputting anything.

I suspect there is an issue with the control feed - the battery light comes on and goes off on the ignition cycle, but when it's really low it doesn't illuminate at all, even when the battery is low/ dead.

I only ever seem to have battery voltage across the battery or alternator, and also on the smaller feed wire.

Does it go to the body module, can anyone confirm, and any idea or advice? I have changed the alternator for a new one of the correct type, but it's made no difference.

 

[koalar]

one of the few times, you need to check the earth on the gearbox
you really need to disconnect it. Its possible for water to enter and break some of the braid. But you will feel this. Clean up the connections with wire wool and a scouring pad.

same with the connection on the chassis rail

 

[koalar]

there is also a Black connector near the battery

check for corrosion

on my car its to the left of the battery D04

 

[Rollcage]

I ve changed all the positive earth leads as it had some horrible quick release battery terminals fitted, they all look fine.

 

[koalar]

I dont believe there is a feed wire. My understanding is small wire only controls the warning lamp, but I could be wrong.

Has this car always had this problem ?
did it start after removing the quick connect ?

the battery negative is normally quick release

 

[koalar]

positive earth leads

negative ? take its a typo

 

[koalar]

measure the voltage on the battery terminals

engine off
engine on, idling
engine on, headlight on
engine on, over 2K revs

move the volt range to 2 volts
measure from the battery negative terminal to the alternator case

report back

 

[Rollcage]

I dont believe there is a feed wire. My understanding is small wire only controls the warning lamp, but I could be wrong.

Has this car always had this problem ?
did it start after removing the quick connect ?

the battery negative is normally quick release

It was apparently like it when I bought it (cheaply). Previous owner advised me he'd changed the alternator, and it had what looked like a new battery. Obviously it seems he was aware of the problem, as the car just runs down the battery until it won't start.
I've changed both the battery terminals to original ones, I'll try and find a pic of the ones it had, not that it matters.

Thanks for your help so far, I'll do some more on Saturday morning, battery is off and being recharged at present.

 

[Rollcage]

Had these on it when bought.

 

[koalar]

the battery light comes on and goes off on the ignition cycle,

Not sure if I read this correctly

The battery light should be on when the ignition is on

it should stay on, until the engine is started

with the small lead disconnected from the alternator and the ignition switch on there should be battery voltage at the wires end

 

[Rollcage]

Not sure if I read this correctly

The battery light should be on when the ignition is on

it should stay on, until the engine is started

with the small lead disconnected from the alternator and the ignition switch on there should be battery voltage at the wires end

Yes, that's what I was meaning - the light is working as it should on startup, but doesn't come in at any other point, even when the car is running with a battery without enough charge to actually start the car.

 

[koalar]

Yes, that's what I was meaning - the light is working as it should on startup, but doesn't come in at any other point, even when the car is running with a battery without enough charge to actually start the car.

disconnect the little cable measure its voltage with the ignition on

 

[Txuchin]

Alternator has two connections, a thick cable that goes to the starter motor and another thin cable that corresponds to the excitation of the generator.
It is possible to check that the alternator is working correctly by connecting a cable from the battery positive to the excitation contact, passing through a 20W brake lamp, for example.
If in these conditions the operation is correct. There is a problem with the external alternator control circuit: Blown fuse, poor contact somewhere, or faulty ignition key.

 

[koalar]

Alternator has two connections, a thick cable that goes to the starter motor and another thin cable that corresponds to the excitation of the generator.
It is possible to check that the alternator is working correctly by connecting a cable from the battery positive to the excitation contact, passing through a 20W brake lamp, for example.
If in these conditions the operation is correct. There is a problem with the external alternator control circuit: Blown fuse, poor contact somewhere, or faulty ignition key.

Correct if you are bench testing

But isn’t it simpler just to disconnect the small cable, switch on the ignition, and measure the volts. If theres battery voltage, Jobs done. No battery voltage and it needs repairing.

 

[Txuchin]

Yes, totally true, but a bad contact in the excitation cable can appear to be a correct measurement, but a malfunction.

 

[Rollcage]

OK, so there no voltage to the feed wire, which obviously isn't good, so is my problem.

A charged battery gave 12.9 volts off the car, 12.5 at idle and 12.3 with headlights on, same at 2k rpm.

 

[Rollcage]

Also, with the feed wire disconnected I'm getting no warni g light at all, either with ignition on or when running.

 

[koalar]

OK, so there no voltage to the feed wire, which obviously isn't good, so is my problem.

A charged battery gave 12.9 volts off the car, 12.5 at idle and 12.3 with headlights on, same at 2k rpm.

correct

without battery voltage, with ignition on, on the smaller wire the car will not charge.

 

[koalar]

broken wire or fuse is the most likely, let me pull up the circuit diagram

 

[koalar]

is the wire yellow. and red ?