Bosch alternator with D profile plug 

Nearest to rounded side. Labelled L on alt.

Not sure but what I would like to know is their are two terminals I think they are + and - or is the regulator negative earthed ? What reading should I get from the terminals when the ignition is switched on and is this circuit fused and if so what is the fuse location and number . 

Thanks to anyone who can give me this info. 👍

They're not + and -, they are L and DFM, if you're talking about the thin wires into the two-way connector. No fuses involved.

L is the exciter wire which should show 12V or a little less with ignition on. 

DFM is a feedback signal to the engine ECU telling it what percentage of available output is being used. Depending on the ECU, this will probably sit at 12V or 5V when not connected to the alt.

 

What problem are you working on? Does the battery light come on at ignition on?

Edited 21 March, 20215 yr by Wino

The battery went dead I did the normal tests and concluded that the alternator was not working no output when engine running being a bit lazy I bought a new alternator that did not solve the problem . Luckily they took it back . So the alternator fuse is intact and all terminals clean .

Does the battery light come on with ignition?  A very common fault involves wires breaking at a plug/socket connection in front of the gearbox. If the blue wire breaks, the battery light no longer comes on at ignition on.

Edited 21 March, 20215 yr by Wino

Sounds like it . The battery light does not come on when the ignition is on .

 

 

Sorry to be a bozo this plug socket connection in front of the gearbox is going to be hard for me to locate because I don't know where the gearbox is 😂 I would be really grateful if you could give me a little more direction . Thank you 😊

Just out with the dog, will link you to a thread with pictures when I get home. 

Brilliant . Thank you 

Scroll down to about halfway down the page here: load signal alternator cable - Skoda Fabia Mk I - BRISKODA

The working pictures are of my Polo, but I think your Fabia will be very similar.  There's a possibility that the connectors will not be in the same order on that bracket, but just look for the black 2-way connector pair with a blue wire broken.  Both wires may well be broken.  Mend that/those wires and all should be well again.

Thank you again the pictures are perfect . I checked the brown and blue wires with my voltmeter and got no reading from either with the ignition on so now I'll check the connector plug ! 👍👍👍

It's me again sorry . Could I do a further test by running a wire direct from the battery + to the blue part of the alternator Excitor plug .

To be honest I'm wondering if I can bypass the circuit and solve the problem that way . I'm getting on a bit and have no equipment for getting under the car !

I doubt there's any need for further testing. It's such a common failure I think it's almost certainly the busted wires. 

See if you can get a photo through that slot in the undertray, if yours has one there like on Polo?

 

If you frigged it with a permanent live it would flatten your battery when the car wasn't running, and if it were ignition switched it would also need a diode in series. Easier to maybe get a friend or professional in to mend the existing wiring.

Ok true . I'm just being a wuss . There isn't a small window in the under engine cover . I'll just get hold of some ramps and take the cover off . Thanks again 👍

The fabia is pretty much the same as wino's polo pictures apart from the fabia has an undertray with no open slot in it so you will need to remove the undertray.

 

The wires usually break very close to the connector so its easier to cut the plug off and just bridge across with solid wires. 

 

 

Ok true . I'm just being a wuss . There isn't a small window in the under engine cover . I'll just get hold of some ramps and take the cover off . Thanks again 👍

Thank you 🦆