Thought I would share this fix to a long standing issue I have recently resolved.
After transplanting a Skoda 1.9 AEF into my 1.6 CS 2 yrs ago the shut off solenoid ... we'll just wouldn't... when ignition key turned off !
It would however... shut off with key ... but only with the ignition light feed terminal from the alternator disconnected.
But that " temp " (2 yrs ago) fix = Leaving me without an ign light and the voltage regulator without an ign live supply - resulting in big jumps from 0 to 14.5 v charging (not good)
Problem traced to = alternator back feeding through ignition light energising the solenoid with just a few volts enough to hold it open.
Soloution = inline diode wired into the feed to ign light circuit from alternator.
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Sounds simple but took me ages to work out - hope this might help anyone transplanting engines with different alternators.
Hope this explains clear enough
Matt - brighton