Generator gave up the ghost

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Greg Spreeman
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Joined: Fri Mar 14, 2008 9:47 pm
Location: South Orange NJ

Generator gave up the ghost

#1 Post by Greg Spreeman »

So, got the car all shiny and was going to my first car show in some 3 years. Drove down the hill some 4 blocks to the gas station and filled it up with new gas. Took off for the car show and as I kept getting to little hills here and there the engine just didn't have any horsepower. Felt like it was fuel starved. Got out, looked at everything but figured it might just have some clogged jets in the carbs. Problem got worse and worse. Getting to and staying at 3K was difficult at best. Pulled over and had the car idling. Was idling just fine but, I was seeing some shiny bits coming from around the pulley. Shut it down and am guessing I burned up a generator bearing. The rear half of the pulley was apparently stripped of it's notches by the debacle and was seized against the generator. The front portion of the pulley was freely turning so I didn't see any heating issues.

Questions:
- With the shaft freely spinning but basically disconnected from the rear half of the pulley where it has notches to lock in place while I pull off the 36MM nut, how do I get the nut off?
- I remember back in the day I had issues with the right size of the generator and remember ordering the wrong size. How do I determine the right size? Is there a part number stamped somewhere on the generator?
- Just putting it out there, what are the odds I burned up a bearing but the guts of the generator are all just fine and dandy? I know, not possible without tearing it apart. Just looking for guesses.
Greg Spreeman
1965 356SC Coupe
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Martin Benade
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Re: Generator gave up the ghost

#2 Post by Martin Benade »

Reach around and grab the fan with a gloved hand and put the wrench on the pulley nut, it should loosen fairly easily.
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Dave Erickson
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Re: Generator gave up the ghost

#3 Post by Dave Erickson »

The hub for the pulley halves has flats you could put a wrench on, if you can get the rear pulley half out of the way.

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Steve Proctor
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Re: Generator gave up the ghost

#4 Post by Steve Proctor »

When the rear pulley goes, often the result of the old <10 shim debacle.
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Al Zim
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Re: Generator gave up the ghost

#5 Post by Al Zim »

DISCONNECT THE BATTERY, Then Find a quiet place in your garage then remove the generator with the cooling fan. You are probably not going to rip the pulley off the generator in the car. With an impact wrench you can remove both the 36 MM nuts and evaluate the condition of the generator. More than likely it needs to be replaced. If you are going to rebuild ask the rebuilder what they are going to put new in the generator. Everything should be replaced except the housings and the hardware. Find out where the armature is coming from and if they can rewind the fields with plastic coated insulation on new copper wire. You should replace the regulator also. This is not a cheap deal! Zim
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Patrick Ertel
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Re: Generator gave up the ghost

#6 Post by Patrick Ertel »

OK, I"m a little bit of a cheapskate and an optimist. There is a good chance the pulley was put on wrong, with the wrong number of shims and the belt too tight or too loose. I've run into this more that once.
Use vice grips or whatever other method you can to get the nut off. Sometimes having someone hold the fan while you turn the nut will work.
If you can't find a way to get the nut off with the generator in the car, you'll have to take the generator/fan unit out.

I would buy a battery powered impact wrench and a 36mm socket to get the nut off. (You will never regret owning a good battery impact gun.)
Once you have the carnage cleared away, check the bearing - spin the armature and try to move it up, down, sideways, in and out. You can do this in the car if you managed to get the nut off. If it doesn't jiggle or grind, you probably just wrecked the pulley. Get new pulley halves, probably a new hub, woodruff key, and the right shims. Put it all back together properly and see what you got. You might get lucky. Even if the generator is trash, these are all parts you will have to have.

If the bearings are loose or noisy, but are not so shot that the armature won't turn easily, try doing a motor test. If they are so bad you can't even do a motor test on the generator, replace the bearings before you do anything else. It's easy to do once the fan/generator unit is out of the engine. You need 2 Fafnir 202KDD or similar, shielded 15x35x11mm bearings. US made Fafnirs are available on Amazon for $10 to $20. While you have the armature out give it a good look for signs of overheating, like shiny bits of solder thrown out of the commutator. If you see solder thrown out of the commutator, your generator needs a full rebuild. If it looks good, polish the commutator with fine emery paper and put in new brushes (they are less than $10). After you put the bearings in, do the motor test. Put 6 volts across the armature and field terminals (with + on armature) and see if the generator turns (motors). It won't turn fast, but if it turns, the generator is probably OK.
If you want to be more assured do this:
RGEM.jpg


Clamp the generator in a vise. Put a volt meter between ARM and Ground. Connect the Field to Ground. Wrap a rope around the pulley and spin it in the clockwise direction (looking at the pulley end) as fast as you can without jerking the generator out of the vise. You should get a voltage reading. In the picture above I was able to get 2 volts out of a 90mm 12 volt "unicorn" generator at probably 50 -75 RPM.
If all this fails, you'll need to go back and take Al's advice - but you'll have the new pulley parts and a battery impact gun - and a wise man once said, "You will never regret owning a good battery impact gun."
Patrick Ertel

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