Greg,

The way the system works in all alternators or generators, the need for something called a voltage regulator takes the inverse relationship you know about and kind of makes it a side effect. There is an energy storage device, the battery, in the system, and a source, the alternator. The combined effect of these components makes the phenomenon you described in the beginning actually occur, that is, as the resistance increases the alternator and the battery try to maintain the voltage in a fixed range. This causes the fuse to pop in the set of circumstances you and then I described. IF there was only a battery, and it was sized so it could only barely maintain the load alone, then Dave would be correct, and as resistance increased, the amperage would decrease. Since we have a regulated source, and it is regulated on the Voltage feature (which is kind of what a battery is, provided it is of sufficient rating), current will be a consequence of the load. If the Voltage is fixed and the load is 100 Watts, and then Voltage is kept fixed and the load goes to 200 Watts, then the only thing that can accomplish that is an increase in Amperes. In the lead acid battery of the size and rating to start a car, especially a Diesel, the Voltage is regulated by the chemical reaction and the number of cells wired in series. Once you exceed the current rating at 12 Volts the Voltage will droop and Dave's scenario takes over. For a circuit that has a light on it, the fuse will blow before that happens.

The voltage regulator is designed to limit voltage, not boost it, so the alternator has to be designed to make the minimum Voltage required to run the full load of the electrical system when the engine is idling. This means the Voltage will climb, as well as the available power, as the rpm increases. The alternator is designed to limit this Voltage rise so it is not linear, and the regulator can be sized to fit under the hood. As loads are added while driving the car, the alternator usually absorbs it, and at highway speeds, usually has lots of margin. At idle the situation is not so robust, and if you have a Voltmeter, you may see the Voltage flicker when the blinkers go on and off, when you step on the brake, turn the fans on, etc.

The dip in Voltage that accompanies the increase in demand for Amperes is an artifact of how the alternator, regulator and system are designed to work over the full range of possible operating conditions (high rpm - no load, high rpm - full load, idle - no load, idle - full load). If the Voltage continued to droop to say, 5 Volts, the Amperage would not continue to go up as at 5 Volts you just could not get the power out of the alternator. The lights would glow dimly, and the fans would slow down and so on.

I don't know if this has helped or not, but I hope it has. Jim

Jim, I can not imagine a better answer than what you gave. That is the kind of overview and component relationships description that really helps...... I hope you don't mind, but I plan on addressing all my future electrical questions directly to you.... Thanks, Greg

Poor Ducati,

He must be completely lost in this discussion, am I right Ducati?

Well, Alex Greg and Jim and I have given a pretty good account of car electic theory and practice, and I hope that you will re-read my primer on circuits which will let you troubleshoot shorts on any vehicle. Perhaps a few more questions from you will help you figure it out.

It kinda sounds like you have a piece of solder connecting the + wire to the ground wire. If this is a front turn signal, you should have three wires to it. One will be brown, yes? the other two will be some colors/stripe, etc.

Here is what you should do. Go to local PNP and steal (make that "borrow") another connector. Snip off the wires a good 3 inches from the connector.
Then crimp on the matching wires to your car. Done. It will function perfectly. Oh yeah, borrow some fuses from donor car as well. If you don't have a crimp plier and solderless connectors, GO BUY THEM!! You will always use them for the rest of your life.
Anyone here will agree, and if they don't they cannot be trusted and are definetly from Pakistan, or Uranus, or somewhere...
Hey Presto.

Ducati, if you are asking me (Ed) about what happened to the Jag?

Now on to soldering ! Since we agree that solder is worth its weight in gold... when you get those matching wires.... take some flint sand paper and spread them into a fan shape and fold the little piece of sandpaper and pull it across the copper wires a couple of times.. they should be really pretty....you have done this to both matching ends that you are going to put together..... BUT WAIT... YOU MISSED A STEP.... first put an appropriate size piece of shrink tubing...on one of the wires up out of the way..., both in hole diameter and length.. remember it will shrink and that you have to be able to get it up over the wires you are going to twist together end to end... just integrate the fans and twist....then if you are out under the car,,, a really nice touch is the little piece of flat solder already cut which you can just wrap around the joint and use a match to melt into it... or you can use a soldering gun... some are even 12 volt... after you melt the solder and it has cooled... and it is always important to keep the wires stationary until the solder has fully cooled... then you pull the tube of shrink tubing down and center it on the joint.. then you use another match... or really hot air gun with the curled adapter on the end... to shrink the tubeing onto the wire... you will not have to worry about corrosion at this place for many years, if ever. I said flint sand paper so you don't use wetordry,,,silicon carbide because it leaves particles that corrode stuff,,, this is why you don't sand distributor points with it.

Leathermang

Thanks for the tip about the sandpaper!

I think another alternative would be some flux which would clean the wires as well.

Re shrink-tubing; I have found some tubing with glue on the inside!! It is the clear glue you use with a glue gun, but is coated on the inside of the tubing. When you shrink the tubing with a heat gun, the glues flows and creates a super strong, waterproof joint you will never have to worry about.

More questions
 

While we're on the subject of corrosion in electrical connectors I have two more questions to throw in the mix.What is the best method/chemical to clean the pins and sockets?What is the best way to prevent further corrosion?Thanks in advance:)

Ed , the reason I mentioned the sandpaper is that Forest Mims III , who wrote all those helpful Radio Shack electrical do it yourself books said that most wire , even the fine multiwire we use on automobiles has lacquer on the individual wires in the bunch that makes up what we are calling one wire... and that for a good solder joint that needed to be removed... I do not think rosin based flux removes that and we sure don't want to use acid core solder for wiring joints... I expect some wire experts to jump in here and say that is not true about the fine wires... but the wires look physically much brighter, the same effect as taking off lacquer from copper in other instances and it is not going to hurt doing it... so I always do it. I think Mims says to use a match to burn off the lacquer from the ends....but then you would want to get the soot off so I just use the sandpaper to start with.
I have never run across any of the Shrink with Glue... but I am cheap and get my shrink tubing from computer stores in three foot sections,,, instead of from auto stores in those expensive packages ....
Another item that I have found useful for protecting solder joints is Liquid Electrical Tape... not as good as shrink ,,, but some hard to reach and/or temporary places I have used this with great success. Greg

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.

Dave, I did not take your statements as being critical.... I have already said that I do NOT know about electricity... I am trying to figure out more of it.. but most of the time the discussions get large due to the definitions,, which are pretty deep with electricity... One of my biggest pleasures with Diesels is the lack of an electrical ignition system... :) ...As is probably obvious I mainly repeat things I have read other places.. which does not make them necessarily proper for where I repeat them... that is where more knowledge than I have really helps... I did want people to know that I was not making them up out of whole cloth... even if I might be misplacing them with respect to their viability in a particular setting ..... Greg

Well, I traced the problem. The battery was not holding a charge. Also, numerous poor connections. It appears that the fuses were rotating in their holders and ovalated the connectors. Replaced the entire unit with a junkyard part for $40.00 and bought a new battery. Everything now works - signal light, window...it was all due to the fuse box being worn. Froze my fingers. I hate it that my garage is full of bikes and other cars so I have to work outside in the rain & snow, in the worst weather we have had in over five years.
Oh well, its all fixed now...and everyone's advice was put to good use. I really appreciate it.
Time to throw some logs in the fireplace & pour a stiff shot of rum.

Ducati, DO NOT get rid of that fuse box.... We ARE going to want to examine it further after you saying " It appears that the fuses were rotating in their holders and ovalated the connectors."
What do you think was making the fuses rotate ?
I can not find ovalated in the dictionary, do you mean ovulated, were they female ? If you had female (short) fuses I can understand you having troubles with them. Greg

Am I getting my Mords Wixed up?
"Oval"ated...as in It Went All Oval Shaped. Or was that "Oblonged"?
Yeah.Thats the ticket. My fuse box went Oblong. (or "Blonged" for short)

Ducati, It was not fair of me to do that to a Canadian, Your words were fine, I needed to say that in order to deliver the punch line... Greg

Dammit, Kenny, yes you can borrow it, but it's called a Multipolar Dioptic Infared Tesla Coil Widget (or MDITCW for short), not a Multipolar Dilithium Crystal Testosterine Coil. We put a lot of effort into this diagnostic tool, so please honour that by remembering what it is called.

Greg and Dave, and all the others following this thread,

I apologize to Dave for implying his application of V=IR was not the whole story, and to Greg for possibly misleading him. After reading what I wrote and spending a minute to run some calculations for the circuits and system, I have to admit Dave's response is correct. The power drawn is equal to the amperes raised to the second power times the resistance, and in that relationship it is apparent that lower resistance draws more power. Sorry about the misleading dissertation on the circuit with corroded terminals or connections.

I will be more careful not to confuse power, or load, and resistance when I try to offer explanations in the future.

Jim