Hello there,

 

I’ve had this issue on my fabia vrs for a while now. After doing quite some extensive research, everything points to the DFM wire that runs from the alternator to the ECU. I’ve cut back this wire fairly close to the alternator plug, and as far as I could go under the battery tray obviously getting rid of the problematic connector. I’m getting 12.5v on both pins when disconnected from alternator with ignition on (common to get similar voltage at both pins on a diesel), and have also got a battery light on the dashboard with ignition on. 
 

Any help or suggestions would be greatly appreciated :)

Possibly a problem with the voltage regulator part of the alternator, is it original as far as you know?

What voltage do you see across battery terminals with engine running?

The whole alternator was replaced around 12 months ago with a second hand one. I don’t have any issues with charging/power randomly dropping either, and the issue was there before the alternator replacement. 
 

Voltage shows 14.40v at battery terminals with engine running, and 12.70v with engine off I believe. I replaced the battery with a new yuasa one last year. 
 

Alternator plug shows 12v exactly on DMF & 11.80v on the blue wire***

The voltage regulator also has clear signs of damage to the casing, so the connector is held in place with a cable tie currently 

That photo would make me think it's a connection problem, right there. 

 

Thank you, I’ll definitely try a new voltage regulator then. 
 

Am I right in saying that if the DFM wire was broken, then I’d have 0 volts right? 

27 minutes ago, Ryanjev said:

Am I right in saying that if the DFM wire was broken, then I’d have 0 volts right?

Yes, I believe so.

 

Could you maybe solder the wires straight onto those pins coming out of the regulator?

Would spade connectors do? I’ll definitely try that, at least then I’ll have a definite answer that the issue is on the ECU side if it doesn’t end up being successful. 

Fitted an alternator that I picked up from a breakers yard, and problem solved! No more traction control light and lumpy idle  Thank you again. 

Well done, always nice to hear of a good secondhand part solving a problem.  👍