PeachParts Mercedes-Benz Forum - View Single Post - Electrical trouble; replace Alternator, Brushes or Voltage Regulator?

dpetryk · #23 01-29-2002, 09:36 AM

Hey Greg, thanks for the clarification. I mis understood what you were saying before. You are right. As the load increases (more current is drawn) from an alternator, its output voltage does fall off a bit. So I see what you were trying to say. At full current load the voltage will be at its lowest. An a lightest load the voltage will be at its highest. These are true statements.

The voltage regulator's role is to adjust the field current in the rotor to produce the desired output voltage for any given load and RPM conditions. They do a great job but nothing is perfect and so the voltage does vary a bit.

It seems to me that there is some confusion about what happens to a circuit that has connector with a corroded contact in it. Given any circuit, the current drawn by that circuit is determined by the circuits total resistance and the voltage across the circuit.

Ohms law states I=E/R.

I = Amps
E = Volts
R = Ohms

So if a circuit has 10 volts, 1 ohm of resistance then the current will be 10 amps. Now add the corroded connector in the circuit. Give it a resistance of 1 ohm. The resistance of the circuit is now 2 ohms. 1 for the orginal and 1 for the coroded connector for a total of 2 ohms. The current in the circuit is now only 5 amps. Adding any resistance to a circuit will only cause a decrease in current and any fuse in the circuit now has less risk of blowing. Fuses blow because of "short" circuits. A "short " circuit is a curcuit that has less resistance than it should have and thus more current. Short means that it is short on OHMS, or not enough OHMS, making higher current than is was designed to have. The fuse is there to keep the wires from overheating and catching fire.

Now the heat produced at the site of corroded connections, thats another chapter. Dont get the two issues confused.

I mission here is not to be critical of anyone, but I see people making statements about electrical systems that make it obvious that they dont really understand whats going on. Im am only trying to help my fellow MB enthusiasts.