OK; I'm a complete novice; I bought this old truck (a '48 F-1), it runs, and I'm having a ball, but what is the difference between an alternator and a generator? This old truck (with a 239 flathead V-8) has a generator, but the previous owner converted it to 12 volts. I have seen pictures from this forum of similar F-1's with alternators (the only difference as far as I can tell between an alternator and a generator is the shape!!! Generators are more tubular, and alternators look short and fat. What they do differently I don't know!!!) . Today, my two month old battery wend dead.....twice. A quick jump and I was up and running, but just to be safe I replaced the battery. Then I got thinking, what if the generator isn't generating enough. Could that be the reason a relatively new battery lost it's stuff? How would I even check? The old 6 volt guage on the dash (run through a voltage reducer) says it is charging, but is it accurate? If I needed a new generator what would I even ask for? The ones at Dennis Carpenter are for 6 volt '48's. My truck is 12 volt, so I assume the generator is 12 volt. Where would I get one of them??? What about alternators? What would you get and how would you make it fit, and is there an advantage to upgrading to an alternator?

HELP Please!!!!

 

Welcome to the forum jreilly57; There are some suppliers selling Alternators in Generator housings so you can keep the orginal look intact. There are some on this forum that will argue the point that the Generator is just as good as the Alternator. They will both get the job done, it's just if you plan to run a lot of acessories and you need a higher amp output probably 60 amp and above you need an alternator. I personally feel that Disc brakes and an Alternator is a must upgrade for a daily driver. If you plan to make it a trailer queen it really doesn't make any difference.

 

Hooking up an accurate voltmeter would be helpful; there's a little digital voltmeter from Schumacher for about $20 that plugs into a cigarette lighter jack. Expect around 13.8 to 14.4 volts when the engine is at driving speed.

Just about any 12V generator that fits should work; try an old wrecking yard that's been around for a long time. But, it could well be the regulator; those seem to go bad more often than the generator.

Advantages of an alternator: it starts charging at a lower RPM than a generator, and has more output (current) capability. Disadvantages: it doesn't look as good, and you've got to come up with a mounting bracket (but you can probably buy one someplace).

I changed my truck to an alternator after 3 strikes against the generator (1. undercharged; 2. bearing failed; 3. overcharged). I made an F-shaped bracket from 1/4" flat bar to replace the generator bracket on the 223 six, and used the common-as-dirt 61 amp Ford alternator.

 

An alternator generates AC power - has slip rings to draw the power off the armature, and diodes to convert the AC to DC current. A generator generates DC power - uses brushes and a commutater to draw the power off the armature and does not need diodes.

The way these devices create power is too complex to explain here - and all you need to know is that an alternator is much more efficient and generates much higher current. A generator may produce 25 amps where an alternator would produce 75 or 100 amps under the same conditions.

That and it is possible that too many short trips in a row will not allow a good working generator system enough charge time to keep a battery charged.

If your generator system is producing 13.5 volts or more measured across the battery at a fast idle (say 1200 RPM) I expect it is working about as well as it can.

There are lots of ways to replace the generator with an alternator, but it will take building new mounts and rewiring your truck.

I have a complete 12 volt generator system out of a 59 F100 I will give you if you want to pay the shipping. I don't 100% know if it is good - but it looks like it should work. I never ran it on the truck. PM me if you are interested.

On edit: Sorry guys, you had not replyed when I started this post - I agree with what you all said.

 

You're already converted to 12V so I'd definitely go with an alternator. They are more efficient and easier to replace. If the wiring scares you, get an aftermarket one-wire. It is very easy to wire up...no regulator to fool with.

Vern

 

Well I hooked up an inexpensive volt meter, and everything seems to be charging as it should. I think I'm good to go for now, but will eventually upgrade to an alternator in the years (or months) ahead. Does anyone know a source that has the alternator and bracket that I would need for a flat head? Hey Willie, thanks for the offer of the 12 volt generator system, but like I said, everything seems to be working now. I would have sent you a direct E-mail, but the system would not let me E-mail directly until after 15 days!!!!! Oh well! Thanks again.

 

I bought a complete 1-wire and slingshot set-up from Certified Electric, fit perfect, and works great on my 8BA (with car engine narrow sheaves)

 

Just google flathead alternator bracket and you'll find them.

 

J,

Look here: http://www.alternatorparts.com/Alter...brackets_1.htm. I used the A200 bracket on my 223 and it worked great.

John

 

Ditch the generator, go with the alterantor.

Bruce

 

57jreilly:

How do you know that it is charging? What is the voltage? If it is 12 or 12.5 Volts, you are likely just measuring your battery voltage. See if your reading changes between the engine running and engine cut off. If they are the same, you aren't charging. You should be charging between 13 and 14.5 Volts.

I like the alternator because it can produce 60% its power at idle versus 0% for a generator. At high speed, generator output goes down due to the centrifugal force pulling the brushes away from the commutator (compressing the springs behind the brushes). The full current output of a generator passes through these brushes. Generators are RPM limited due to the large rotating mass of the armature. An alternator has the windings on case (stationary) and the field is on the rotor. Since the field current is small, big brushes are not required.

Both generators and alternators produce alternating current. The commutator on the generator armature functions as the rectifier. As the armature and commutator rotate, they way the brushes (one ground and one output) make and break contact creates a DC output.