Quote:
Originally Posted by glatt
And this is the voltage. In other trips, the voltage remains steady at around 14 volts, but on this trip, it was fluctuating.
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Voltage in that last attachment (18 Feb) is ideal voltage for all vehicle electronics. Ideal voltage is typically anything from 12.6 to 14. Apparently voltage is a little higher (maybe 14.5) on 18 Feb implying the battery required more recharging current. Which is the alternator working just fine.
On 19 Feb, the first thing that concerns me is the idle dropping to less than 750 RPM. That should not happen. At 750 RPM and lower, the alternator really does not output much current. In fact an alternator often outputs near zero current if RPMs are well less than 800. (BTW, maximum output current starts at maybe 1500 RPMs which means racing an engine any faster does not recharge a battery any faster).
A sudden marked voltage drop on 19 Feb could be a drop much lower than the graph indicates. But that typically would not cause problems as long as voltage remains above 9 volts. Battery (without alternator) should provide enough power. However, is there any reason why neither alternator nor battery maintains above 9 volts? One possible reason is an intermittent ignition key switch. Or an intermittent relay that should but does not hold battery connected.
500 RPMs is a defect. During those 500 RPM periods, was the engine not surging or stumbling? Fact that the engine idled at 500 RPMs is itself an engine defect even if the engine did not stumble. A perfect example of viewing a 100% defect even though the engine appears to be working just fine (not stumbling).
So an interesting question. Is low voltage somehow causing the engine to idle below 800? Or is idle below 800 causes a significantly lower voltage? An example of trying to solve a closed loop system.