Quote:
Originally Posted by btwilson86
Unless I'm completely wrong, the alternator is not controlled by the ecu. It has an internal voltage regulator in the alternator. Also, the voltage you reported at idle is too low, it should still be 13.5 volts. As engine speed changes the available current will change as well, however the voltage should remain constant if the wiring and alternator are both working properly.
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Should be and commonly is are two different things. Most of the MKIII's I've worked on (except mine after rebuilding harnesses) have a significant drop when loaded heavily... I'm not saying it's proper or optimal. That's beside the point though, the point was that the ECU won't fail until the voltage drop a LOT further then the spec 13.2v to 15v.
No idea who said anything about the ECU being controlled by the ECU.