load signal alternator cable

[thecuist1]

Yes the other anomally was my Voltage dropping to 2v when I have the blue wire connected  would be interesting to see if yours was the same. I think we have reasonably verified that 50ma should be enough to fire the alternator but i'm still baffled by the voltage drop. Connecting directly to the battery would also have made sure the alternator was getting 12v wouldnt it?

[thecuist1]

That would make sense, presumably the blue wire sends a signal back to the battery light via the control module to verify that the alternator is outputting 12+ volts. I wonder what the path is from the blue wire through the alternator. Given that I replaced the voltage regulator and that made no difference, maybe there is an issue with the rectifier part of the alternator? I also tested the diodes and they seem to be functioning correctly though. 

Edited 8 November, 2022 by thecuist1

[Breezy_Pete]

1 minute ago, thecuist1 said:

the blue wire sends a signal back to the battery light via the control module to verify that the alternator is outputting 12+ volts.

Yep. On these the connection to the battery light/LED is indirect, data transmitted to clocks module as opposed to a physical wire, but same effect.

[thecuist1]

Hmm well I'm leaning towards a weird alternator fault, probably the next step is to pull the alternator again and either get it bench tested by a specialist or just buy a new one and hope. I hate throwing somewhere in the region of €150 at a problem and hoping but I doubt specialist testing would be much cheaper. If you can test your voltages with blue wire connected that would be interesting, its the last anomaly that we haven't cross checked. I understand that it could be a bit of hassle though,  if its positioned similar to mine the exhaust and heat shield prevents easy access to the plug connectors. I wish my alternator was positioned the same as on the diesel, there was no way I could remove the voltage regulator without removing the alternator. Thanks very much for your input thus far.

[Breezy_Pete]

Access isn't too bad on my Polo, Will probably just stab the blue wire with a needle to get the connected/ignition-on voltage.

Wish you were closer, I've probably got a spare alt you could have tried.  

Edited 8 November, 2022 by Breezy_Pete

[thecuist1]

Yes being on the west coast of Ireland is a bit of a nightmare for motor parts to be honest.  My local motor factors just told me there are 4 variants of that alternator and they couldn't supply one which is odd. I can buy online but postage and returns can be a pain but I have seen one for around €100 delivered but  I'll wait for your voltage reading b4 ordering. 

[Breezy_Pete]

I see even lower voltage than you,  1.2V with a needle poked into the back of the connector along with blue wire.

Demonstrates that the current limiting resistors are doing their thing (and so dropping most of the voltage) and that the resistance of the field coil is low.

[thecuist1]

Wow well there you go, who would have thought a 12v circuit could drop nigh on 11v and still be functioning correctly,  guess I will go ahead and order a new alternator and hopefully that will resolve the issues. Thanks again for your help I will come back and report once I have fitted the new alternator.

[thecuist1]

Hopefully final update on this issue. I purchased a brand new alternator and once fitted the car is now running fine and battery is charging at the correct 14.5 volts.  Thanks for all your help Breezy Pete.