In part 3, I asked the following questions.... If we had a few diodes that were burnt out, would this cause our L circuit voltage to drop and illuminate the alternator lamp? On THIS vehicle (Cavalier) no.... On other vehicles it will if output voltage of the alternator dips too low. Low output caused by open or shorted diodes shouldn't have any affect on the enable portion of the regulator circuitry. Could we use the Generator (F terminal) duty cycle information to help determine if we had defective diodes or a bad stator? The duty cycle reported by the F terminal will be higher if there are problems with the stator or diodes. However, it would also be higher if we have a shorted (internally between cells) battery. So I guess the answer would be yes and no... What would happen if the F circuit became grounded while the engine was running? The alternator output would continue on it's merry old way. Below you can see what happens to output voltage as I ground out the F circuit.
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Another very fast check to see if the
regulator has been enabled is to measure field
current going into the field winding on the battery cable. KOEO,
the field current comes from the battery. It doesn't hit the
normal 8 amps because the regulator is switching
so fast. However, with a scope and current
probe, it is easy to see. (Almost as fast as the Tech 2 -) ).
Note that not all PCMs enable the regulator on key-up. |
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