[Mgb-v8] Alternator Questions

[Smit, Theo]

The voltage at the fuse panel and at the alternator output (which should
be at least a 10 gauge wire, probably connected to a large stud on the
back or side of the alternator) should be the same. With the engine off,
it should be in the range of 12 to 12.6 volts. If it's below 11.8 volts
then your battery needs charging; if it's 10 volts or below then your
battery is damaged and should be replaced.

With the engine on (and having blipped the throttle so as to cause the
alternator to kick in) the voltage at the battery terminal, the fuse
panel, and the alternator output stud should all be at least 13.2 up to
about 15 volts. If it's less than 13.2 volts then your alternator isn't
charging. If the voltage isn't the same (or within 0.1 volts) in those
three places then you have a bad ground or power connection in the
system.

If the alternator isn't charging then it's either that the alternator
has worn brushes (if over 100,000 miles on the alt, this is a good place
to start), or the diodes are blown, or the regulator is bad or
disconnected(a good thing to check if the regulator isn't solid state
and/or an integral part of the alternator), or it's simply not hooked up
right. Check that a wire from the ignition 12V circuit is connected to
the alternator (Japanese alternators have a terminal labeled "IG" for
that purpose), and that it does go to 12 volts when the ignition is
switched on.

The voltage at the coil terminals is generally not 12 volts, so whatever
you measure there is not indicative of the alternator condition.

Good luck,
Theo

-----Original Message-----
<snip>

Any help in solving my problem will be greatly appreciated.

Jim Ray
1980 MGB V8/T35 Automatic
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