The Stovebolt Site Forums The Shop Area The Electrical Bay replacing generater

I have a 1947 chevy 1/2 ton with a 1965 283 engine with the old 12 volt generater, as the generater is froze up, i bought a 12 alternater, it only has one electrical post on it, the old generater had two, with a built in regulater, which wire gets hooked up to the new altenater?

If you have a one wire alternator, the wire runs from the alternator to the starter, where the positive battery cable is hooked up.

You do not need the voltage regulator (the black box)that the generator was hooked up to, alternators are internally regulated.

Most alternators are three wires- They have one wire on the back and two spade terminals in the side. If you have a 3-wire alternator there are tons of discussions on how to hook it up on this site, try the search function with the term 'alternator'

Basically the terminal on the rear of the alternator goes to the starter, one spade terminal is hooked to the terminal on the back of the alternator and the other spade terminal is hooked to the ignition switch after running it through a diode.

It seems to me that the ammeter would always show discharge if you hooked it up like that. I would think that the wire from the alternator should go to the terminal on the ammeter opposite the starter/battery connection so you would have some idea that the alternator was working.

Wiring diagram for one-wire alternator.

One adjustment to this diagram: Alternator to ammeter to the starter battery-terminal (the battery cable also goes to this terminal). I also ran a lead from the ammeter to the ignition switch. I used the 10 gauge wires already in the wiring harness.

would the old battery meter in the 1947 chevy work with an altenater or does it have to be replaced with a modern ammeter?

Hook it up like nm51 say,s. The alt contains diods that prevent curent from flowing back in it. The amp gauge will work but will go way over at times do to the increased capacity of the system. Use 10 gauge wire.

I still don't see how the ammeter would ever show charge if you wired the single wire to the starter, thereby bypassing the ammeter. All of the load except the starter and the output of the charging system should go to one side of the ammeter and the battery, by way of the hot wire on the starter, should go to the other. If you wire the single wire alternator to the battery, the battery side of the ammeter will alway be more positive than the load side, thereby always showing discharge. Tell me where my logic is flawed, please.

Tclederman's schematic shows what I described as being correct.

Baldy,

I have edited my posting above. This setup has worked flawlessy for me for 9 years. The battery charges, the ammeter works, the starter works the same as it did with a generator, and there was no need for additional wiring. I used original wires, splicing a few (and not using a few) when I took out the Voltage Regulator.

Tim

So you are saying your schematic is wrong, but if the alternator doesn't go to the load side of the ammeter, how will the load side ever be more positive than the battery side? I was in electronics for for 45 years, and don't see how that could work. Yes, the battery would be charged by the alternator, but the ammeter wouldn't see it.

Baldy,

The schematic is not "wrong" - I just accomplished the same flow of electricty by way of a slightly different routing of wires (to use the existing wiring as much as possible).

Here is what I tried to state (and, this agrees with your statements): Alternator to ammeter; then, ammeter to the starter battery-terminal; then, starter battery terminal to the battery. I also ran a lead from the ammeter to the ignition switch.

The diagram in my earlier post is for a system that has a two leads coming from the battery - one to the starter and one to ammeter. I did not want to buy a new two-lead battery cable (but that would have worked as per the diagram).

Both the diagram and my adaptation have the one wire from the alternator going to the ammeter.

"Alternator to ammeter to starter [battery post]" Thus, the ammeter works and the battery charges, and the starter gets power from the battery.

And, at about 800 rpm the alternator starts charging (800-1200 rpm, depending on the model of one-wire alternator). Once the alternator is "excited" into charging, it will charge at all rpms.

Sorry about my lack of clarity.

Tim

Thank you for the clarification, now it makes sense. Since I view it as a schematic rather than as a wiring diagram, there is really no difference between having two wires from the battery, one to the ammeter and the other to the starter and one wire to the starter and another from the starter to the ammeter. So the drawing is correct either way.

I can see i,m going to like this group, thank you all for the help, by by the way do i need to use a new ammeter or can i use my original 1947 dash gauges? and keep the dash stock?

mohohead,

Did you old 12v generator work with your original ammeter?

My original '54 6v ammeter works fine with a 12v alternator. My alternator is not very powerful, maybe 50 amps. What is the amperage of your 12v alternator?

No reason to replace your ammeter if it works.

I was wrong. I,m sorry.

You guys are right, if you are wiring your alterntor and ampmeter, you need to run the hot wire from the alternator to the ampmeter and from there to either the battery or the post on the footstarter. It should be 10 guage or thicker wire.

Unfortunately an Ampmeter will only tell you the direction of flow in the charging circuit. A voltmeter would be more useful as it tell you the status of your battery and whether your alternator is charging properly.

Does anyone know of someone who makes a voltmeter that will fit in the original guage cluster where the ampmeter should go? I read somewhere a datsun b-210's voltmeter is the same size/shape and would love to find something along those lines..