MGB: Kim re: charging problem

Hi Kim,
Been following your progress. Sounds like an adveture in spite of the 'Lucas Factor'.
I know you said that your generator is new (last year) so maybe this is moot ~ or just too obvious.
Are the brushes contacting the armature properly?
It sounds like such an inane question & I'm sure someone must have mentioned it.
Just thought I'd ask. Reason is, I had to drive my Mini Cooper 300 miles under the same electrical conditons you describe & that was the problem.
Regards, Graham

That's the kind of oddball information we need. Things that shouldn't happen, but someone knows from experiance that they do.

It's been a long time since I worked on one of those generators, but I do seem to remember that with new brushes installed, they would sometimes stick in the holders and loose contact with the armature. I would simply pull back the springs, move the brushes up and down, then replace the springs and problem solved! This could also be an issue if the brushes were slightly too long!

It's worth a try!

We'll be meeting up with Chuck today, and he's got a guy who can look at the generator.

But we still don't seem to be getting enough juice TO the generator. Unless we're diagnosing this wrong. But the meter shows just 12v leaving the regulator at the field terminal, leading us to conclude that the generator isn't getting enough voltage.

But with a new regulator in place, and assuming it's working properly, where could the problem be?

I'm still thinking it must be a loose wire or connection somewhere. I was cleaning up the engine bay before we left, so it's possible something got knocked loose. But maybe that's just coincidence.

Kim: 12v at the field terminal is fine - the most you will ever get is full bettery voltage, so if your battery is a little low, 12v is all you get. The field terminal simply energizes the field coils to allow the generator to generate! Provided there is some voltage, and therefore some magnetic field, the generator should work. Your descrition of the symptoms certainly supports either a regulator or a brush problem and I would lean towards the latter.

However, I have been known to be wrong!

Eric, that makes sense to me too. 12vdc to the fields should be good enough.

Thet's why they call it a voltage regulator. It regulates how much voltage gets to the field windings and that controls the output of the generator, but, if the field shoes have lost their magnetism nothing starts happening anyway. It has to have that little kick in the beginning for anything to work.

John I always shorted mine out at the genarator post instead of the regulator post.

If the battery voltage at the post is 12V, then I would wonder how you would get more than 12V out of the voltage regulator?

I think batteries are 2.2 or 2.3Volts per cell. Each 12 volt battery is made up of 6 cell (6 holes to put water or battery acid in). Taht would give you around 13 to 14 volts total.

Batteries may be slightly over 12v, but not much (ie. 12.2). Your alternator/generator may put out 13-14v which allows the battery to charge (think of electricity as water pressure-you need higher pressure to get back to the battery to charge. Lower pressure will cause the battery to discharge).

While that is kind of true, it really depends on the material the cell is made of and the specific gravity of the cell. Lead-Acid normally will be around 2.0 volts per cell, while Lead-Antimony will read about 2.2-2.3, and Lead-Calcium will float around 2.3-2.5 volts. It is also dependent on the specific gravity of the cell. That is what the little eyedropper type thing is used when checking a battery.

Lithium Cell voltages range around 4v per cell, while Nickel-cadmium will read about 1.4V.