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&*@#]$%_]#[* ... Generator problems...

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ronzet

ronzet

Jedi Knight
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TO LBC Gurus everywhere... Good morning...

So, OK... I have a new (VB) generator and a new Votage regulator(Moss) in my restored/rebuilt '57 A....

I posted a query a while back on the polarization of the system soooo no need to repeat that here....

The generator is marked 'Negative ground' but, per recommendations, I left my electrical at positive ground and polarized the system...

The generator light still glows nicely all the time.. and the batteries discharge so I am sure that the generator is not 'generating'... so to speak....

THE QUERY.... How do it determine if I have melted the generator or the Regulator or ??? I have tried to use a digital multimeter to check the output of the generator but the EMI seems to bounce it all over the place... I will borrow an Analog to test it this week but am looking for advice in the interim...
/bcforum/images/%%GRAEMLIN_URL%%/wall.gif
Thanks...
 
Not a Generator guru (nor do I know a lot about MGAs either), but couldn't you just measure the voltage at another location away from the generator like say the battery or another location?

I mean if you can jump start the car you should be able to measure the voltage to the battery. On a alternator it shold read about 14vdc with the engine running if it's charging. Regardless if the battery reads say 12v and that value goes up when the engine is on then the problem isn't the Generator.
 
I just went through that mess with a new Moss genny. After polarizing the genny I had no better luck as it was still not charging. Turns out to be the VR, and I had shorted the genny. Probably while reversing the polarity, New VR and problem solved, it was a Ford VR by the way per recommendations of an old time Abington worker that my electrical mechanic knows. Parts Shops will tst the genny for you. I don't think a 57A has an alternator does it?
 
It'll be a generator, Mike. Shunting the field and output connectors and reading voltage from there to ground AT IDLE ONLY should yield a 12~20V reading on an analog meter, Ron. NO higher RPM or the field winding or armature winding could suffer meltdown.
 
DrEntropy,

Thanks for weighing in on this... I keep expecting to drive my A but 'tis always something....

I hate to keep buying parts only to screw them up.... What's REALLY embarrasing... I am an EE....I guess not a very good one... /bcforum/images/%%GRAEMLIN_URL%%/rolleyes.gif
 
But Ron, EE's <u>design</u>, they don't maintain! /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
I'm lucky in my <u> </u> job. I get to design, build, <u>and</u> test.
Jeff
 
Consult the factory manual for the testing procedure regarding generators and control boxes. I'd rather not have to type it all out on a mobile device! It's all in there though.
 
Jeff,

Thanks for the words of solice.... still, a schematic by any other name is still a schematic...a difference in potential is still a difference in potential... /bcforum/images/%%GRAEMLIN_URL%%/rolleyes.gif
 
Ron - You cannot use a digital multimeter to get a good reading on a generator. The generator puts out a pulsating DC voltage and a digital multimeter will try to read the instantanious at the moment of sampling, which may be full voltage or zero or anywhere in between. Using an analog multimeter, remove the wires from the two terminals of the generator, jumper the two wires together and attach the negative lead of the meter to the jumpered terminals (assuming that you have repolarized the generator to positive ground), positive lead goes to ground. Start the engine, but don't rev it up, rather slowly increase the reves while watching the meter. A good generator will have an increasing voltage that continues to climb. Do not let it go above 20 volts or it will increase very rapidly to high enough voltage to damage the generator. If the voltage will not reach 20 volts it is bad, even if if it reaches 12 volts and won't go any further, the generator is bad. If you can get the 20 volts out of the generator, then your problem is a bad regulator (it is not uncommon to get bad regulators off the shelf).
Cheers,
 
David,

Thanks for the words of wisdom... I had tried my didgital and found that it bounces all over the place. I have an old analog meter that needs a battery that I will use to test the generator.

I am in the process of removing my gas tank to clean it out (per my recent posting about fuel flow). Once cleaned and re-installed I will perform the generator tests...

ALSO, Dr. Entropy... very nice website link, by the way... a wealth of information.... 'tis now in my favorites...
 
If you get to the paoint of the gen being good, I think the reg can be adjusted. It should be pretty straight foward in any repair manual. Good luck.
 
Ron - The only thing that the battery is used for in an analog multimeter is the resistance readings. All the other scales function fine without the battery.

Yes, the regulator can be adjusted, but it is not a real straight forward procedure and if it is new, you should not have to adjust it to make it work (and will infact void any warrantee by trying to adjust it. If you find that the regulator is bad, you might want to consider a solid state regulator in place of the old relay type units. Bob Jeffers makes a solid state regulator that he puts in the original regulator case so it looks original from the outside. His e-mail address is: bobj20@comcast.net
Cheers,
 
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