Converting a Generator to an Alternator

Better questions will yield better answers. You failed to mention the make/model of the tractor and make model of the alternator you decide to use. Please provide the following:

Tractor make

Tractor model

Tractor gauge type, voltmeter, ammeter, or warning light

Alternator make

Alternator model

Alternator year

Alternator amp rating

Many years ago I converted my old diesel engine charging system on my sailboat. One thing I did learn was that the charge lamp provides a current path for the excitation field of the alternator. It was not just an "idiot light on the dash". B and S are electrically the same point. However, B output can have a IR voltage drop from the alternator to the battery so that point B is not at the real voltage of the positive battery terminal. S carries a very small current and thus senses the voltage a the battery more correctly. I ignored the IR drop in the output cable, used very large 00 size wire, and connected a jumper from S to B. Found a small indicator light at my automotive store and it has been working fine for ten years or so now.

farmal 460

There are alternators available that are commonly called "one wire alternator". These alternators have one wire coming off the alternator which goes to the battery for charging. http://www.alternatorparts.com/FAQ.htm#one%20wire

There are other configurations available with an ignition wire to provide excitation at slow speeds and to provide drive for a charge indicator lamp.

After you choose your alternator, find the appropriate pulleys, belt and build or buy a bracket, all that is left is putting it together and making it work.

If you don't already have the alternator, you can scrounge one, get them off Ebay or from auto parts houses. Just do your research so you will know what to ask for and how to use it.

Have FUN!
TT3

Here's an online tutorial:

http://www.autoshop101.com/trainmodules/alternator/alt101.html

If you are using an alternator salvaged from an older automobile, check to see if it has a separate voltage regulator. A voltage regulator designed for use with a generator will not work correctly with an alternator. Newer alternators have the regulator built into the alternator housing.

Turbotroll's caveat about the ammeter is good advice. If your tractor has an ammeter, and if the current capacity of the ammeter is less than the maximum current output of the alternator, you should either replace the meter or bypass it.

Thirty-eight years ago I cleaned up a generator-to-alternator conversion that had been botched by the service department of the dealership that had sold the vehicle to my client, who had to pay for the job a second time, and a new wiring harness in the bargain. Depending on the age and size of this tractor, the electrical system may be very simple or very complex. If you can find a service manual, read it. It isn't impossible to do serious damage if you don't know what you are doing. Good luck!

You should follow ozzb's suggestion nd diagram it gives you a comprihensive run down on things.

Otherwise 'if pain persists consult your doctor' instead of burning your machine to ground.

The easiest thing is to buy a GM alternator and have a shop install a regulator which is self exiting. Then you have a one wire hook up just the big wire.

http://www.ytmag.com/articles/artint178.htm

http://www.rowand.net/Shop/Tech/AlternatorGeneratorTheory.htm

When I converted a 1935 Ford from 6v to 12v I did use a Delco alternator with the regulator built-in (there are at least two types- get the built-in regulator), then follow the directions by rhandwar, turbotroll3, ...

Understand you will need to change all light bulbs, the radio?, anything that uses electricity, switches will be OK, you should probably start by removing all of the fuses before you start and replace one at a time after you verify each circuit is ready for 12v.

The other item is the ignition resistor. This resistor must be in-line with the "points" in the distributor, if not the points will burn-up frequently. An alternative is to install an electronic ignition (www.pertronix.com as I recall) which can operate on 12vDC to replace the points.

He doesn't need to change the voltage only the generator (dynamo) to an alternator.

We don't even know if he's got an alternator or not yet. If he does have one then might as well try to make it work rather than change it because you suggest it.

Ihartensteiner,

everyone so far is quoting US codings. You dont say where you are so you may also come across european terminal codes.

A typical european alternator would have:-

B+, connect direct to battery (verify cable size is good for full output, as already advised)

D+ or 61, connect to a charge warning light which in turn is connected to the igniton switch 12 V. This provides the initial current to supply the internal regulator to start the charge process. For this reason it is important to use a lamp of 3W. Don't get tempted to use an LED or miss out the warning as you wont get any charge.

W, Tachometer output. I would suppose that if you have a tacho, that it is supplied by a tacho-gen. if so this output will be unused. (If you had been changing an alternator that used the W o/p you would have to look out for the the change in tacho reading if the pulley size had changed).

If this and/or the previous posts still havent made it clear for you then post a photo of the replacement unit, carefully marking the terminal codes and a pic of the makers plate.

good luck

Chas.