Is this an alternator or a generator?

[turnjare]

This photo is from the engine compartment of a 1949 chevy 3/4 ton. the engine is a 1956 235. The truck has a 12 volt battery, is this a generator or an alternator?

thanks,

Jared

[62lwbc10]

That would be a generator

[G&R's57GMC]

This is a Alternator, the thing in the lower left corner.

[mark '87 930]

that looks like a flux capacitor :-)

[turnjare]

Any reason to change to an alternator?

[47 Fasttoys]

A generator is basically a DC motor. The lower the engine RPM the lower the output voltage, When you sit and idle the output voltage is somewhere in the 10 to 11 VDC range depending on the generator. This will keep your truck running fine but your lights will be dim and you will be pulling on your battery a little. When at higher RPM there is no real difference. The regulators will still limit max output voltage on both so you don't overcharge your battery or pop your lights. A alternator on the other hand puts out the correct voltage at any RPM. When the system calls for higher current the alternator can do this also. The alternator is in a smaller package with a higher capacity.
I'm no expert by any means...But I do live at the Holiday Inn.
Rob

[Coupeguy2001]

Those generators are 25 amps. You have to match it with the same capacity voltage regulator.
The later alternators have a built-in solid state regulator, and are pretty much more reliable unless the front bearing fails or you have a direct short to ground somewhere with a heavy wire, and can overload the alternator.
The alternator needs 12 volts to place some current in the voltage regulator that compares the input voltage from the battery, and then biases the field coil to produce the necessary current to charge the battery while running the electrical system.
The alternator and the generator both are a constant potential charging device, in that the regulators have a predetermined voltage goal, and the closer they get to that voltage, the less they charge.
THe alternator can still produce 75 amps if the load is present, and still maintain the proper voltage, but the generator will produce 25- 30 amps, and that's it. If your air conditioner is running, drawing about 55 amps, your battery will be dead in about an hour, less time if you have lights and stoplights working.

[_Ogre]

Originally Posted by turnjare

Any reason to change to an alternator?

not if you stay stock with your electrical system.
adding loads like a killer stereo, electric fan, etc... will need more amps.

[mr48chev]

Ogre pretty well nailed it. not if you don't run a lot of accessories that draw more power than the generator puts out.

There are two issues with running a generator these days. One is as Ogre said above, they don't put out the amps to keep up with accessories that demand a lot of power. Most put out about 30 amps or maybe 35 max. That means if you have halogen lights, a sterio with an amp and or a few other electrical powered items they may not keep up with the demand and cause the battery to discharge as it supplies the power that the generator isn't producing.

The other issue is availability of replacements or replacement parts on short notice. While any good starter/generator/alternator shop can rebuild one if it is rebuildable if you are on a road trip and the generator gives out you may be stuck until you can get yours fixed or get a replacement shipped in. I'd want to make sure it was in top shape before doing any road trips. I am thinking about running one on one car I am building simply because it will keep the car more authentic to the theme that i want to build it to. It's supposed to look like an old two seat boat tail race car that may have been run in the late 30's or early 30's and an alternator would be out of place on it. I seriously doubt that I will drive it more than 150 miles in any direction away from home and it won't have a radio or any other accessories on it so power demands aren't an issue.

If you do decide to go to an alternator at some time you don't need to buy a fancy bracket. Just use an alternator for a mid 70's Chevy pickup and get a 3/8 bolt that is long enough to go through both ends of the stock generator bracket with enough sticking out the back to put a lock washer and nut on. stick the bolt through the bracket from the front and slip the alternator on it and push the bolt through the back bracket. Then push the alternator to the front of the bracket and measure the distance from the back to the bracket and make a spacer that will take up that space. You may have to reverse the bracket on the block to line up the pulleys right but I am not positive on that. I've got three or four 235's running around the country that i set up like that for people.

[franken]

From the look of the things in the pic, if the generator is working, things like brakes are a higher priority.

Get a voltmeter and measure the battery voltage with the engine off, and with it running while giving it some gas.

If the voltage is higher w/ the engine running, you're charging.

If you have a 6V system and a 12V battery, then it sort of depends on how that was made to work...