[TR] [British-cars] Moss Video to test Lucas generator

[Randall]

> I found this Moss video to show how to test a generator but 
> now I am a bit
> more confused than before I watched it.

Not surprising!  The test they show at the beginning would only apply if the
generator was being spun at several thousand rpm.

> ( as this
> appears to be a bench test are they trying to simulate the 
> generator being
> in a vehicle?).

I believe so, yes.

> My thinking is that I should be able to place the generator 
> on the bench and
> spin it at around 3,000RPM and look for a reading in excess 
> of 12 volts.  Is this correct?

Well, there are some caveats.  Most importantly, you should have some means
of either "sneaking up" on the test conditions, or have a load (like a
battery) on the generator.  Otherwise, the generator is quite capable of
generating enough voltage to damage itself.  Lucas warns not to let the
output voltage exceed 20 volts.

You will also need to provide field current; either by connecting the field
to the armature, or to an external power source (like a battery as shown in
the video).

And this test is NOT definitive; a partially failed generator may put out
12v but not enough current to actually charge the battery.

> Is there a simple proved why to test a generator before 
> re-installing it?  

If you are just doing this once, for your own car, then IMO setting up a
reliable bench test is more hassle than it is worth.  Just do a visual
inspection and then, if all appears OK, install the generator on the car to
test it.  Or, find an old fashioned "auto electric" shop and have them test
it for you on their equipment.

BTW, there is a copy of the Lucas "Generator & Control Box tests" booklet
available at
http://tinyurl.com/37voevm
(You may need to create a Gmail account first)

Randall