Technical Alternator charging light

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Technical Alternator charging light

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Can anyone tell me how to check the wiring from the alternator that tells the computer its charging

I know the alternator is charging but the computer isnt getting the signal so the charge warning light is on and I'm getting knock on problems with the power steering.

Thanks in advance. Much appreciate any help I could get
 
The computer will sense alternator charging, not by battery voltage, but by a separate signal wire. This is probably the small wire on the back of the alternator. From Haynes, on the 500 this feeds to the engine management computer, which will tell the body computer, but on the Panda, it feeds to the body computer. So there are choices. I don't have a wiring diagram for the Stilo.

Before computerisation, this wire was fed battery voltage, and earthed through the alternator when not charging, the earth path being broken when the alternator gave an output. I would expect this to still be the same, rather than having an output from the alternator through that wire.
This would need to be tested though. By disconnecting this, and with ignition on, but engine not running, see if there is a voltage at that wire end. A voltage there shows it is workiing as older systems. No voltage may mean no output from the computer, or it is expecting an input to the computer. Testing that is more difficult, and probably involves a voltmeter on the terminal when the wire is connected to the alternator, and with either engine running, or alternator spun by hand, if the drive belt is off. Access is difficult, and potentially risky, with the possibility of shorting things, with burns and fire resulting, or worse, getting caught in moving parts. So take extreme care.

If the alternator is just not sending the correct signal, its internal diode pack is failing. A replacement alternator is the way to go for this.

On both 500 and Panda the main output from the alternator seems to connect to the starter, just as a connection point, to feed back directly to the battery.

You say you know it is charging, presumably with 14v or so at the battery, and the battery not going flat. On the smaller vehicles, Panda, 500 and Punto, the main earth cables corrode internally, creating problems, usually showing as a steering fault initially. No reasson to suppose Fiat used better cables on a Stilo, so would be a good idea to carefully check the earth cable, from battery, to body and engine. Not just connections, but for continuity and resistance. Starter and steering require big currents, whereas charging does not, so a charge can be 'felt' despite poor connections.

The steering will try to work as long as it has enough power. It does not take a message from the body computer about whether to be lazy, it just uses what is available via its own fat supply cable.
The warning lamp is controlled presumably from the body computer, which is not sensing sufficient alternator output. It is doubtful that there are multiple faults, so I think the main cables and their connections are the places to look.
 
I think the Stilo has a separate signal wire (though I'll go have to go and look on mine later to check).

If so, then it must be possible to attach a voltmeter at the alternator where this wire connects, and look for any signs of life... which would answer the question about whether the alternator is producing a signal.

On other forums (Grande Punto mostly) a glowing alternator light and loss of power on the steering have regularly been an alternator problem.


Ralf S.
 
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Yes it has two outputs. A big chunky one which presumably feeds the charge to the battery and a thin one which im guessing is the one that feeds the computer with the 'alternator working' signal.

Both outputs have 14v at the alternator so im pretty confident the alternator is ok.

Im pretty sure its the feed to the computer so the computer thinks the alternator isnt charging and because of that it shuts down the power steering to conserve battery power.

This is further supoorted because if i disconect the power to the body computer (thus disabling the alternator not working shut down power steering circuit) the power steering works.

Im pretty sure the fault lies either in the fuse box near the battery or the wiring between the alternator and the body computer. I just dont know how to test it.

Thanks again for your help. Really appreciate it
 
The computer will sense alternator charging, not by battery voltage, but by a separate signal wire. This is probably the small wire on the back of the alternator. From Haynes, on the 500 this feeds to the engine management computer, which will tell the body computer, but on the Panda, it feeds to the body computer. So there are choices. I don't have a wiring diagram for the Stilo.

Before computerisation, this wire was fed battery voltage, and earthed through the alternator when not charging, the earth path being broken when the alternator gave an output. I would expect this to still be the same, rather than having an output from the alternator through that wire.
This would need to be tested though. By disconnecting this, and with ignition on, but engine not running, see if there is a voltage at that wire end. A voltage there shows it is workiing as older systems. No voltage may mean no output from the computer, or it is expecting an input to the computer. Testing that is more difficult, and probably involves a voltmeter on the terminal when the wire is connected to the alternator, and with either engine running, or alternator spun by hand, if the drive belt is off. Access is difficult, and potentially risky, with the possibility of shorting things, with burns and fire resulting, or worse, getting caught in moving parts. So take extreme care.

If the alternator is just not sending the correct signal, its internal diode pack is failing. A replacement alternator is the way to go for this.

On both 500 and Panda the main output from the alternator seems to connect to the starter, just as a connection point, to feed back directly to the battery.

You say you know it is charging, presumably with 14v or so at the battery, and the battery not going flat. On the smaller vehicles, Panda, 500 and Punto, the main earth cables corrode internally, creating problems, usually showing as a steering fault initially. No reasson to suppose Fiat used better cables on a Stilo, so would be a good idea to carefully check the earth cable, from battery, to body and engine. Not just connections, but for continuity and resistance. Starter and steering require big currents, whereas charging does not, so a charge can be 'felt' despite poor connections.

The steering will try to work as long as it has enough power. It does not take a message from the body computer about whether to be lazy, it just uses what is available via its own fat supply cable.
The warning lamp is controlled presumably from the body computer, which is not sensing sufficient alternator output. It is doubtful that there are multiple faults, so I think the main cables and their connections are the places to look.

Cheers for this Bill

I have put a voltmeter on the alternator output (small wire) with the alternator running and it reads 14v.

The battery voltage is also 14v with the engine running.

Also battery hasnt gone flat over an extended period.

All these seem to suggest alternator is ok.

If i disconnect power to body computer power steering works so presumanly the power steering itself is ok?

I pulled the fuse box apart, then refitted and reconnected the connections and the alternator/battery warning light went out and the power steering worked. Unfortunately i created another problem (lights permanently on) and when i pulled it all apart again i fixed the lights problem but the original one was back.

This suggests the alternator itself is ok, the power steering is ok and the fault lies either with the fusebox or the wiring?

I just dont know how to get to the other end of the small output wire from the alternator.

Appreciate your help
 
I think there have been issues with Stilo fuse boxes, the one under the bonnet, with water ingress. Quite likely it has several dirty or corroded contacts, and disturbing it helps, or creates other poor connections. You might need to clean every connector in the fusebox, or it might work just unplugging and replugging each fuse and relay.

Does the fusebox have its own earth connector?
 
Take a look:
 

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Thanks again Bill. I pulled fuse box apart. There is defo an issue (defo has had water ingress) i really thought id found the cause of my problem. But having cleaned it all and refitted my problem remains ?
 
Take a look:

Cheers for this. Unfortunately im struggling to identify the location of the connectors? Which is the D4 etc and where actually (physically) is it etc.

The schematic is a bit like the london underground map and doesnt reflect where things actually are on the car.

Appreciate it though. Thanks bud
 
D4 is inside the fusebox. Follow the small wire, D+, from alternator to pin 19 to bodycomputer M1.
 

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D4 is inside the fusebox. Follow the small wire, D+, from alternator to pin 19 to bodycomputer M1.



Cheers any idea which/where the d7 is?

So i should have continuity between the small wire on the alternator (is that the D+ ?) and the wire that connects pin 19 on the body computer?

Any idea which connector the pin 19 is on? There are a few connected to the body computer

Thanks again for your help
 
The computer will sense alternator charging, not by battery voltage, but by a separate signal wire. This is probably the small wire on the back of the alternator. From Haynes, on the 500 this feeds to the engine management computer, which will tell the body computer, but on the Panda, it feeds to the body computer. So there are choices. I don't have a wiring diagram for the Stilo.

Before computerisation, this wire was fed battery voltage, and earthed through the alternator when not charging, the earth path being broken when the alternator gave an output. I would expect this to still be the same, rather than having an output from the alternator through that wire.
This would need to be tested though. By disconnecting this, and with ignition on, but engine not running, see if there is a voltage at that wire end. A voltage there shows it is workiing as older systems. No voltage may mean no output from the computer, or it is expecting an input to the computer. Testing that is more difficult, and probably involves a voltmeter on the terminal when the wire is connected to the alternator, and with either engine running, or alternator spun by hand, if the drive belt is off. Access is difficult, and potentially risky, with the possibility of shorting things, with burns and fire resulting, or worse, getting caught in moving parts. So take extreme care.

If the alternator is just not sending the correct signal, its internal diode pack is failing. A replacement alternator is the way to go for this.

On both 500 and Panda the main output from the alternator seems to connect to the starter, just as a connection point, to feed back directly to the battery.

You say you know it is charging, presumably with 14v or so at the battery, and the battery not going flat. On the smaller vehicles, Panda, 500 and Punto, the main earth cables corrode internally, creating problems, usually showing as a steering fault initially. No reasson to suppose Fiat used better cables on a Stilo, so would be a good idea to carefully check the earth cable, from battery, to body and engine. Not just connections, but for continuity and resistance. Starter and steering require big currents, whereas charging does not, so a charge can be 'felt' despite poor connections.

The steering will try to work as long as it has enough power. It does not take a message from the body computer about whether to be lazy, it just uses what is available via its own fat supply cable.
The warning lamp is controlled presumably from the body computer, which is not sensing sufficient alternator output. It is doubtful that there are multiple faults, so I think the main cables and their connections are the places to look.

With the small wire removed from the alternator it has no voltage (with ignition on but not started)
 
Just wading in here but your alternator seems to be putting out enough voltage at 14v but my thoughts are "is the body computer actually seeing that voltage correctly" because if it's not enough then the current hungry power steering won't be allowed to operate and you'd get an alternator failure light and no power steering. Something easy you could try is plug in almost any diagnostic tester that will read the voltage at the diagnostic port ( or you could read it directly with a multimeter if you know the pin numbers for ground and batt+). If it's not showing the same 14v voltage at the Body Computer (BC) as you're seeing in the engine compartment then there's your problem, the BC earth. From very cloudy memory I think that earth point is near the fuse box but I don't have the Stilo wiring diagrams any more.

You may well have to clear any fault codes too before it's happy again so, if you're unable to read and clear any fault codes which could give a clue, then disconnect battery for 1/2 hour and see if that clears them for you


Good grief, it's been a while. I'm impressed there's Stilos still going


Decks
 
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D4 connector

I've read loads about the D4 connector and think it might be (at least part of) my problem.

I've read all the info in the guide section and loads of posts.

Is it possible to separate the connector and get to the individual wires?

Thanks for any help
 
Just wading in here but your alternator seems to be putting out enough voltage at 14v but my thoughts are "is the body computer actually seeing that voltage correctly" because if it's not enough then the current hungry power steering won't be allowed to operate and you'd get an alternator failure light and no power steering. Something easy you could try is plug in almost any diagnostic tester that will read the voltage at the diagnostic port ( or you could read it directly with a multimeter if you know the pin numbers for ground and batt+). If it's not showing the same 14v voltage at the Body Computer (BC) as you're seeing in the engine compartment then there's your problem, the BC earth. From very cloudy memory I think that earth point is near the fuse box but I don't have the Stilo wiring diagrams any more.

You may well have to clear any fault codes too before it's happy again so, if you're unable to read and clear any fault codes which could give a clue, then disconnect battery for 1/2 hour and see if that clears them for you


Good grief, it's been a while. I'm impressed there's Stilos still going


Decks

Cheers for this. I'll try to read it again tomorrow when my head isnt as mashed from it but im certain its something to do with that.

I wondered if there might be a fault in the connectivity from the alternator (through the d4 connector/connectors under the engine fuse box or the wiring.

I have actually messaged you as you clearly know you stuff but wasnt even sure i was doing that properly.

Ive spent about 5 days on it!
 
Just wading in here but your alternator seems to be putting out enough voltage at 14v but my thoughts are "is the body computer actually seeing that voltage correctly" because if it's not enough then the current hungry power steering won't be allowed to operate and you'd get an alternator failure light and no power steering. Something easy you could try is plug in almost any diagnostic tester that will read the voltage at the diagnostic port ( or you could read it directly with a multimeter if you know the pin numbers for ground and batt+). If it's not showing the same 14v voltage at the Body Computer (BC) as you're seeing in the engine compartment then there's your problem, the BC earth. From very cloudy memory I think that earth point is near the fuse box but I don't have the Stilo wiring diagrams any more.

You may well have to clear any fault codes too before it's happy again so, if you're unable to read and clear any fault codes which could give a clue, then disconnect battery for 1/2 hour and see if that clears them for you


Good grief, it's been a while. I'm impressed there's Stilos still going


Decks

And big thanks
 
Yes the D4 connector is hidden under the fusebox and it's a simple block connector so you can get access to either side. Check out the earth node point there too as it's very close to the fusebox
 
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Just wading in here but your alternator seems to be putting out enough voltage at 14v but my thoughts are "is the body computer actually seeing that voltage correctly" because if it's not enough then the current hungry power steering won't be allowed to operate and you'd get an alternator failure light and no power steering. Something easy you could try is plug in almost any diagnostic tester that will read the voltage at the diagnostic port ( or you could read it directly with a multimeter if you know the pin numbers for ground and batt+). If it's not showing the same 14v voltage at the Body Computer (BC) as you're seeing in the engine compartment then there's your problem, the BC earth. From very cloudy memory I think that earth point is near the fuse box but I don't have the Stilo wiring diagrams any more.

You may well have to clear any fault codes too before it's happy again so, if you're unable to read and clear any fault codes which could give a clue, then disconnect battery for 1/2 hour and see if that clears them for you


Good grief, it's been a while. I'm impressed there's Stilos still going


Decks

Error code was

Alternator status (from CAN) not being recharged

A couple of times ive got it to work (more luck than anything) after disconnecting fusebox and cleaning it and refitting connectors but ive not been able to replicate it or make the fix permanent

But ive not reset that error code so maybe need to try that
 
Yes the D4 connector is hidden under the fusebox and it's a simple block connector so you can get access to either side. Check out the earth node point there too as it's very close to the fusebox

Any pictures? I know there is an earth strap fastened to the inner wing (which is ok) but is that the same as the earth node?

Thanks again.

I was meaning if i can actually split the plastic connector as im thinking maybe they arent connecting properly to the underneath of the fusebox
 
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