Right now I see two different threads running here regarding Electrical systems that are dealing with alternators and generators. Unfortyunately I see a lot of stuff that is just plain wrong. It is no wonder to me that people are having so much trouble. Somewhwere along the line I am guess ing people have had a lot of bad experiences and have wrongly concluded thatsomething they did at the same time caused the problem. SDo, justb for the sake of clarity I'd like to make a few points here.

1. Alternators or the egnines and electrical systems will not be harmed if disconnected before or during running the engine. I have done this hundreds of times and I have even run dirt track stock cars with systems that actually electrically disconnect the alternator everytime the the throttle is opened.

2. Disconnecting the negative battery terminal while running will shut down the engine with either an alternator or generator.

3. Disconnecting the positive battery terminal will not shut down the engine with an alternator if it is charging.

4. Depending on the type and preset values in the regulator, (internal or external), the charging voltage output of the alternator should be 13.5 to 14.5 volts for a twelve volt system.

5. The 6 volt amp meters in older trucks will work fine with alternators if they are hooked in series with the alternator output going to the battery and the rest of the system. Voltmeters need to be hooked with the pos. terminal to the 12 V. pos. someplace after the ignition switch and the neg. terminal to ground or battery negative terminal.

6. Alternators are superior in every way to the old generators.

7. If you want to retain your old 6 volt system but want an alternator, it is possible to design and build a simple solid state regulator for an external regulated 12 volt alternator. I have done it several times.

8. Alternators will place no load on the system from the output terminal when not running. They have a rectifier bridge circuit inside that will not permit the backflow of current unless the diodes are shorted out. If that is the case thet wont work to charge your system.

I have restored many old Lincoln welding machines with Continental Red Seal Flat head engines that had 6 volt systems and generators. See www.pvpmedia.com/wfs.htm . I have done it with both mag and point and coil systems. The simplest way to convert is to buy a suitable GM type one wire alternator. I buy them at Auto Zone for about $55.00. I suggest you get a new one so you are not screwing around with something that may be defective or soon to go bad. Besides that they just look better.

If anyone has any questions feel free to ask here or with PMs or e-mail. I'd be glad to help. It bugs me to see so many are having trouble with this stuff. I have been playing around withn this stuff for 50 years and I think I can help.

 

hard to get some headed the right way if they read different somewhere

 

There's plenty of info about disconnecting battery cables on alternator-equipped cars on the 'net. This is one of the better ones:
RWD - Serviceman Disconnected Neg Cable While Engine Running-Questions

 

Thanks for the input Dave - glad you stepped in.

As with most things I think a lot of us have opinions based on our own individual experiences and whatever formal training we may have had - and I think everyone will agree that you never know it all or stop learning. Sometimes, there is more than one right answer. But one thing I do know about myself is that I find trying to analyze an electrical problem is enough of a challenge when you are standing there with all the right gear and watching what happens. Trying to analyze it by e-mail then express that picture you have in your mind into words is almost impossible. That's why we have manuals, and people in shops who work solely on those systems.

I think you could really help Mike out in the two posts (which I think are the same problem) and I'll be watching to see how it turns out.

 

So what you are saying is to connect the red wire to the black wire? LOL !!!!

Dave, you just made so manny people aware of the truth. I think that rumors just spread and people get scared. Good to know that i can count on you for my questions later when i wire things up. Thanks!!!!!!!!

 

i'm a wiring idiot , so i generally will get someone { pay them !!!} to do it . i know it's simple stuff but for some reason or another i just seem to have difficulty grasping the concepts behind it . so the more i see and here the more i pick up on , not that i'll ever trust myself with it ..............

 

when i was looking at insurance for my truck i was told that most people put in claims when they burn up there truck after wire changes or repairs. It made me think about it!

 

A little follow-up here... Thanks for the kind words from everyone. I considered the fact that I was running the risk of seeming like a know-it-all when I started this thread. That is not really a goal I aspire to. I just hate to see someone doing the wrong thing and ending up ruining something or having a fire. Like I said, their are a lot of little tricks I have learned over the years that I can tell would come in handy for you guys. I don't know how soon I can get it up but I am considering putting up a little webpage with some simple tips and diagrams that answer most of the common questions.

I have noticed that a lot of guys buy and install those pre-made wiring systems and harnesses. I'm sure that makes a good job and can look professional. The big problem is that those things are big bucks and often don't totally apply to the application you may be dealing with. In lot of cases I have read here, people aren't needing to go to the extreme of doing a complete replacement job. Remember, we like to do it cheap.

One other thing I noticed about my original post is besides the fat-finger typing screw-ups, I failed to mention that even though the amp gauge in older vehicles will work, most of them are only rated to 30 amps and will just peg-out. They have gone to using volt meters because a lot of the moderm alternator systems push 100 amps or more. I had a Ford Contour that had a 95 amp alternator which was actually standard through out the modle line. When I do a system I prefer to install both voltage and amp meters. Of course this is of little good if you don't know how to interpret what you see.

I don't always see all the posts that pertain to all these things so if any one wants to ask questions feel free to PM me. I would also be interested in hearing all the most common problems so I can later address them on a small webpage. But, here's the kicker, there could already be webpages up out there that take care of this problem. If anyone knows of any let us know. There is no use in re-inventing the wheel.

 

Roger,
You are quite right... The most common cause of fires and electrical damage is wiring practices. They either pass the wiring throuh rough cut holes in sheet metal or use wire too small for the job. Fusing is also important. They are fooled by the fact that even though a job is poorly done it works at the beginning. When they start to put it to use things happen then it's too late. A good example is these damn places like Wal Mart and Circuit City who put monster audio systems in and don't have the slightest idea about common safe wiring practices. They just drill holes everywhere and end up causing shorts and leaks. It seemes that the only major qualification required for a person to be hired as an instaler is the fact that they once put a radio in a car.

 

I hear that!

When I bought my truck, it was a fantastic deal....not so much because the price was only $1500, but it had every piece of hardware on it, and it was in great shape rust wise.

But oh baby, did I learn a lesson about the proverbial "PO" This was a guy who threw a timing chain and because of his pass under motor mounts didn't remove the pan and clean prior to installing new. I figure he got about 100 miles before the engine ate itself, then he parked a new unfinished restoration next to his house for 25 years before I rescued it.

This guys wiring was so bad and so piecemeal that I just stripped the whole truck - every thing- and started over. I used the next size larger wire; soldered the ends before clamping on connectors; put every item on it's own fuse; got all new firewall grommets; and created a power point document wiring diagram for future reference.

When I pulled out that wiring, there were over 200 splices and crimp connectors and five or six burned spots - it was a disaster waiting to happen. And it seems like just about everything he did was like that. 98% of my restoration has been undoing what that idiot did when he "restored" the truck in the late 70s.

I prefer an Amp gauge. They seem to show problems more quickly. When I rewired and re engined, I bought an 80 amp one wire alternator and was a little concerned about, first, running a wire with that kind of current through the firewall into the cockpit; and second if the stock gauge would handle it. My gauge is the original (intended for the 6V system) induction loop type that the wire just passes through.

So, I got some fuel hose and slit it then bound it around 2" of the wire as it passed through the firewall as a chaffing strip, then through the gauge loop. It seems to work really great. I don't have any high draw items, but at night, lights on, in the rain, with the heater going, it will push up about 1/3 of the way.

Now the truck is solid and the wiring secure.

And Dave, don't worry about sounding all knowing. We know WE AREN'T, and when dealing with the VOODOO of electrical systems, it's always nice when tho old "witch doctor" steps in!

Here's a before and after:

 

It has been my understanding that you need to have the positive lead connected so as to have a voltage feed to the field windings in order for it to charge. Without it how can the alternator charge and how can the ignition system sustain itself? What am I missing?

Gear Up

 

The current draw for a 12v system is much less than for a 6v, so the only potential problem with the stock ammeter is if you really drain the battery and the alternator kicks in at full output. Even then, since there isn't a direct mechanical connection between anything and the needle, it just pegs and sits there. Not like a mechanical oil gauge that has a linkage to the needle.

My PO was fond of using band-aids instead of electrical tape.

 

[quote=Sandidande;6086194]I hear that!

And Dave, don't worry about sounding all knowing. We know WE AREN'T, and when dealing with the VOODOO of electrical systems, it's always nice when tho old "witch doctor" steps in!

Here's a before and after:

Thanks for the kind words. It looks like you did a great job of straightening that mess up. It's a wonder somebody didn't get their feet tangled up in that mess.

 

First of all let's cover the basics... In an altermator there really is no field windings like a generator. The armature acts as a rotating electro-magnetic field with a current supplied through the slip rings and brushes. Often there is a terminal marked as field or "F" but it is connected to one of the brushes feeding the slip rings. But, you are correct in saying that there should be a positive voltage applied to it. The other slip ring is connected to ground and it often has no seperate terminal because the alternator has a common ground terminal or gets it's ground through it's mounting. The current required for the field to work correctly is approximately 10% 0f the total output of the alternator. This voltage is usually applied directly from the ingition terminal on your ignition switch or by a relay that gets it signal from that terminal. That way the field is supplied only when the engine is on. In the self regulating one wire type alternators the output terminal is ALWAYS connected to a 12 volt pos. source directly from the battery. Starting the alternator rotating will create a minor amount of current due to residual magnetism in the armature. It is just enough to be sensed by internal circuitry which by means of solid state switching circuitry will make a connection to the circuitry that supplies the regulated voltage to the rotating field of the armature.

If you have an alternator with a field terminal that requires an external regulator, DO NOT hook a 12 volt positive feed directly to it!!! This will cause the output voltage of the alternator to go very high. It is possible to go up in excess of 100 volts. This has the potential to smoke a battery and burn out stuff in your electrical system. The external regulator controls the amount of voltage to the rotating field by sensing the output voltage of the alternator.

I hope this helps you with your problem.

 

This is correct but you are forgetting that adding all the stuff that a modern vehicle or an updated vehicle has will greatly increase the load on the system. Therefore the current load is usually in excess of what was required of the old systems. So long as the amp meter is the induction type with the pass-thru loop that the wire just goes through without making an actual connection. However, all amp meters are not that type. Some use a an internal coil paralleled with an internal or external shunt. Modern 12 volt systems do operate in current ranges far in excess of the old 6 volt system because of the extensive use of electrical energy in moderm vehicles. the old generators were only good for about 30 amps max. Even small cars rountinely have alternators that are rated for 100 amps. Get a good amp meter and check out the current on a modern vehicle after starting on a cold day. You will probably be surprised to see how much current is produced.