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Re: [Mgs] Generator front bearing.

To: Simon Matthews <>,MGS <>
Subject: Re: [Mgs] Generator front bearing.
From: Barney Gaylord <>
Date: Tue, 21 Apr 2009 14:27:45 -0500
At 10:57 AM 4/21/2009 -0700, Simon Matthews wrote:
>.... I purchased a new armature for the generator in my MGA. I 
>recently got around to replacing the armature. .... after a mile or 
>two, I could hear a new noise from the engine compartment and on 
>returning home, the generator was very hot.
>Any thoughts on what I might have done wrong?

If you bought a new armature, we might presume the old one was burned 
out.  Burned out armature is commonly caused by a faulty regulator 
relay in the control box causing the generator to run at maximum 
unregulated output at all times.  This can drive generator ouitput 
somewhat higher than 20 volts at road speed, and the resulting 
over-current can burn out the armature.

Any time you change a generator or control box you MUST check the 
output of the generator.  Polarize the new generator first, and test 
the generator output before connecting it to the wiring 
harness.  After verifying that the generator works, connect it up and 
do a running test of the regulated output to be sure it peaks out 
around 16 volts max (at the dynamo output terminal) and no 
higher.  If the regulated voltage is just a little off, slightly high 
or low, then the regulator relay only needs a little adjustment.  If 
it runs to much higher voltage at speed the control box is bad with 
faulty regulator relay, and needs to be replaced.

Bottom line is, a faulty $40 control box will burn up a perfectly 
good $100 generator.  If you don't change the faulty control box it 
can burn out the new generator as well.  It will often get hot enough 
to melt solder and break up the commutator segments.  Before that 
happens it might cook the oil out of the rear bronze bushing causing 
that to fail and allowing the armature to drag on the field coils 
making lots of loud screaching noise.

Barnay Gaylord
1958 MGA with an attitude
Support Team.Net

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