[What you are doing is, "assuming" there is a problem. I am saying there is nothing wrong by, "deductive reasoning."
So the "SYS" light you guys are talking about is just a purdy little light soley for the driver's entertainment?
You are correct... I meant "voltage." I don't have a copywrite date on this book. This is an invaluable copy called, Automobile Guide, by Frederick E. Bricker. It covers early, to modern automotive components.I paraphrased the voltage sentence from the book. So as not to ask permission from a quote.
Gotcha
Let us say the voltage reg. was faulty. The higher in rpm you go, the more current is made.
Absolutely wrong! The alternator is a combination of an AC producing generator, an AC-to-DC converter (the diode rectifier), and a DC voltage regulator. The voltage output of the AC generator WILL increase with RPM, as will the DC output of the diode rectifier assembly, and the regulator's job is to keep the overall output of the alternator at a constant voltage. The amount of current drawn from the alternator is soley dependant on the amount of load (resistance) placed on it, from Ohm's law: Current = Voltage/Resistance.
The battery itself has an internal resistance, lower battery charge = lower internal resistance = more current drawn from the alternator. Turning lights on adds parallel resistance, which means more load, which means more current drawn from the alternator.
If the reg was bad, you'd see the needle peg at, and past 18V. Therefore, the voltage reg is doing it's job.
Maybe, maybe not. It's impossible to predict what WILL happen if the regulator goes bad. Now if the regulator were "removed" from the circuit...then what you describe is the output of the diode rectifier circuit.
Think of it this way. It's a Vette, with gobs of electronic components. Every component needs different amounts of current. Here's the battery already at a low charge rate from sitting, and the starter motor takes the biggest draw of current. The battery's voltage drops even more!
No argument there.
Now the engine is running, and some of the electronic components need at least 12 Volts of current to funciton. The battery needs even more! What does the voltage reg do? It increases the current to feed the battery more than the 14.+ voltage it would normally need if it were in a good state of charge.
You are using the word "Volt" as a unit of measurement for current...this is completely incorrect. Voltage is expressed in volts, Current is expressed in amps. Voltage is defined as the potential difference in the quantity of electrons between two points. Current is defined as the quantity of electrons flowing through a conductor.
A fully charged battery has an abundance of electrons at the negative terminal. When a resistance (or a load) is placed across the battery terminals the electrons start to flow from the negative terminal to the positive terminal, thus creating current. If these electrons are not replenished (via the alternator) then the potential difference of electrons between the negative and positive terminals (the Voltage) starts to drop.
This is why most auto shops have the reputation they do. You are ready to change out the alternator because you think that is the problem. Which is what an amature mechanic at a shop would do. I see a car with a low battery from sitting. It's that simple.
I believe what I suggested was to simply keep an eye on it.
I'm using my empirical knowledge, and a little logical deduction with the excellent information DWC has related us. Bottom line, I expect the battery to go south because of the sitting factor. If the car is a high milage car, then brushes are about to be needed. If that's the case, just replace the alt. with the new battery, and there should be no problems. If the car has low milage...battery only.
Bill? You're up.
Sitting for a week at a time should NOT cause any harm to a battery, unless there is a parasitic drain that is discharging the battery below 9 volts or thereabouts. Overcharging however WILL damage the battery (alternator output voltage too high). A discharged battery should NOT cause an increase in the voltage output of the alternator, but it WILL require the alternator to deliver more current (due to the decreased internal battery resistance).
This discussion has gone beyond the scope of helping out DWC. If you want to continue to debate basic electronics theory, then let's do it in a separate thread or off-line.
To DWC I'll say again...dude just keep an eye on it.
Jack, the "flickering" is probably in fact do to a slight fluctuation in the output of the alternator...you're voltage gauge is just not fast enough to reflect the rapid fluctuations. I've noticed this on my car as well at idle.
Bill
