Quote:
Originally Posted by chevysilverado
What does the RPM have to do with the VR?
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Anthropomorphizing a bit... The voltage regulator doesn't produce voltage. The voltage regulator requests the alternator to produce one specific set voltage. At low / idle RPMs even a health alternator may have trouble producing all the voltage requested. At 2000 RPMs a healthy alternator will have no problem what so ever producing any voltage in the correct range and beyond. If the voltage regulator has an internal short and is requesting 18 volts, you'll see that (excessive volts virtually guarantees its a bad regulator). If the voltage regulator is weak and only requesting 13.3 volts you'll see that.
Back in the days when voltage regulators were a separate, external component, standard on car test procedures (as opposed to bench test procedures) dictated that when voltages were out of spec. you temporarily swapped in a known good component (usually the regulator, because it was less work) and retested. If the voltage irregularity was corrected, the swapped component was bad. If not, the other, unswapped component was bad.