starting issue. help please.

[sepulchrave]

I am surprised that nobody has so far suggested checking the common failure point wire from alternator that runs under the power steering pump - Wino has all the pictures. The red light on dash going out is not a reliable proof that the alternator is being given the required current to start producing a charge current.

 

Because it's a 1.4 MPI and the charging system isn't load controlled by the ECU, that's why.

[ty1986]

I'm not getting the red battery light come on, it's only managed to come on for split second then again when was at home on the same journey the other day when it was totally flat. I'm gonna get a new alternator SEPULCHRAVE hopefully it's that. Poiutyre111, is that the wire that has a small wire coming off it before it disappears under the battery tray. Have you got a link please to the pics. Gonna go mad with cleaning all the connections for battery and alternator this weekend too.

[poiuytre111]

Must admit I didn't know that the 1.4 MPI alternator doesn't need an initial trickle of current to the rotor to start the ball rolling - all that I have seen do. Does the alternator only have one fat output wire then ?

[Breezy_Pete]

No Mk1 Fabia has a charging system that's 'load controlled by the ECU'.

 

The DFM wire is loading information sent from alternator to the engine ECU, not instructions coming from the engine ECU to the alternator.

The blue wire is the one that when broken means the alternator doesn't always start up correctly and usually results in the battery light not coming on when ignition is on (before starting).  All alternators have this wire.

 

I think in this case it does look like the alternator itself is at fault, but there's no harm in examining the relevant wiring at the usual breakage point.

See here and links within.

[poiuytre111]

No Mk1 Fabia has a charging system that's 'load controlled by the ECU'.

 

The DFM wire is loading information sent from alternator to the engine ECU, not instructions coming from the engine ECU to the alternator.

The blue wire is the one that when broken means the alternator doesn't always start up correctly and usually results in the battery light not coming on when ignition is on (before starting).  All alternators have this wire.

 

I think in this case it does look like the alternator itself is at fault, but there's no harm in examining the relevant wiring at the usual breakage point.

See here and links within.

 

Having had this set of symptoms myself and having changed the alternator for a new one to no good purpose, I would agree that checking wiring is best done first.

[sepulchrave]

No Mk1 Fabia has a charging system that's 'load controlled by the ECU'.

 

The DFM wire is loading information sent from alternator to the engine ECU, not instructions coming from the engine ECU to the alternator.

The blue wire is the one that when broken means the alternator doesn't always start up correctly and usually results in the battery light not coming on when ignition is on (before starting).  All alternators have this wire.

 

I think in this case it does look like the alternator itself is at fault, but there's no harm in examining the relevant wiring at the usual breakage point.

See here and links within.

 

Best simple explanation I could find for how contemporary charging systems work:

 

http://www.autoelectro.co.uk/how-it-works-alternators

[poiuytre111]

Best simple explanation I could find for how contemporary charging systems work:

 

http://www.autoelectro.co.uk/how-it-works-alternators

A key point not mentioned there in relation to the early charging system is that it is the initial current through the dash bulb that creates a magnetic field to start the charging process. If that circuit is not complete then no output current is produced. On my problem mk1 tdi I ran a wire direct from the blue wire at the alternator to the battery positive via a resistor so that it drew 50 ma so about 240 ohms. This was enough to restore normal operation until I got around to fixing the wire.

[Breezy_Pete]

Best simple explanation I could find for how contemporary charging systems work:

 

http://www.autoelectro.co.uk/how-it-works-alternators

I don't think Mk1 Fabias are contemporary enough to have this bit "Many modern vehicles adopted a load request type charging system with the introduction of smart charge systems and CANBUS systems which are now widely being used. These systems are controlled by the vehicle ECU. As the vehicle demands more load the ECU sends a signal to the alternator requesting it to start charging" 

On the two vehicles I've looked at, unfortunately not including any diesels, the DFM signal is definitely coming from the alternator, you can still see it with it disconnected from the ECU if you provide a suitable pull-up resistor. 

The info is used by the engine ECU and connected systems (e.g. Onboard supply control unit) to adjust control parameters for the engine to smooth idle fluctuations etc. and to reduce loads on the system by switching off inessential systems like seat heaters etc if things look grim according to the onboard supply control unit.

 

In terms of what current the alternator is generating moment by moment though, that's 100% locally controlled by the voltage regulator module.

[ty1986]

This is getting really technical for me now. So I will check the blue wire coming out the 2pin plug for loose connection in the plug. Also when battery is charged from its trickle charge I will see if battery light comes on when ignition is on and then goes out or weather it don't come on at all when ignition is turnt on. You guys are so helpful, I'm getting myself so stressed out lol. Most prob end up being something simple.

[sepulchrave]

Most prob end up being something simple.

 

Like a faulty alternator perhaps? 

[ty1986]

Yea lol most probably. Can get a new alternator from ECP for £79 with a discount

[Tech1e]

Yea lol most probably. Can get a new alternator from ECP for £79 with a discount

That's cheaper than I can just had a look. Make sure you get the right one as there are four options. AME w/o A/C (5pk pulley), AME w A/C, (6pk pulley) AQW w/o A/C (5pk pulley) and AQW w A/C (6pk pulley).

[ty1986]

Ok so have just been to the car and when turn the ignition on no battery light illuminates. Everything else comes on then goes off.

[Tech1e]

So check your wiring.

[Breezy_Pete]

Aha!

Find break in blue wire and mend it.

[ty1986]

I'm gonna do that tomorrow or Sunday. Best starting from alternator and working back? Maybe giving it a wiggle here and there

[Breezy_Pete]

Might be able to see it from the top on an 8-valve, if you take off the engine cover, there's not much in the way of looking down at the bracket where the two-way plug/socket pairs are if I remember correctly (that's by no means guaranteed).  TMB will probably be along soon to confirm/deny, with a bit of luck.

Edited 22 July, 2016 by Wino

[ty1986]

Yea can see the plug into alternator and the the other small connection at the bottom of the engine too from under the bonnet. Unplugged the alternator plug with blue and brown/red and run a wire from blue to earth point, turnt ignition on then the battery light came on.

[Breezy_Pete]

Hmm, that suggests the blue wire isn't broken.

 

Maybe the alternator brushes are worn out (or stuck in their holders) so much that they aren't reaching the slip rings?

 

Not sure how easy it is to remove the voltage regulator/brushpack module on an mpi alternator to examine/check?

[ty1986]

Easier replacing with new alternator then, it's looks pretty dirty the alternator anyway and looking in the handsome the wires look green and cruddy

Edited 22 July, 2016 by ty1986

[Breezy_Pete]

Yeah, unless you can find a matching secondhand one easily somewhere locally, it may be the simplest solution.

[ty1986]

This is the one from ECP. After I enter my registration it comes up with this.

[TMB]

Might be able to see it from the top on an 8-valve, if you take off the engine cover, there's not much in the way of looking down at the bracket where the two-way plug/socket pairs are if I remember correctly (that's by no means guaranteed).  TMB will probably be along soon to confirm/deny, with a bit of luck.

 

Yes you are right. I run mine with no engine cover anyway.

[TMB]

This is the one from ECP. After I enter my registration it comes up with this.

 

What's your engine code and does it have A/C?

[Tech1e]

This is the one from ECP. After I enter my registration it comes up with this.

Is yours an AME engine?

Just put your reg in and get the same four options. It flags up there are multiple options for your reg.