The test is a good representation of the voltages encountered on load, but
since the motor is off load it is hardly a full test, so I don't really see
why they bother. Using 12v on both will not do any harm and would reveal a
hard fault on either solenoid or motor, but not reveal any marginal faults,
only a full load test will do that. I have heard some people refer to a
'growler' test that sounds like a rig that does put the motor under load and
possibly measure torque, using 10v in this case would confirm the solenoid
is OK at on-load cranking voltages.
The extra terminal (it may have a smaller spade than the solenoid operate
terminal) is to feed a full 12v during cranking to a ballasted (6v) coil,
typically found on post-74 or so MGs, to boost ignition.
----- Original Message -----
From: Jason B Lonon <firstname.lastname@example.org>
Sent: Wednesday, July 26, 2000 9:04 PM
Subject: testing starter motor
> Hi. I'm trying to test the starter motor to see if it's working or if it's
something else that's causing my MGB not to crank. I've removed the start
motor and solenoid (M418G Pre-Engaged) and want to test it. If I'm reading
the Haynes Manual correctly, I'm supposed to hook a 12 volt supply across
the large battery terminals and then apply a 10 volt supply to the small
> Questions: Why 10 volts? Can I use 12?
> There is another terminal marked IGN that is not hooked up to anything on
my car, what is it's purpose?
> Sorry for bugging you, but the manual is not very clear in these
> Jason B. Lonon
> '72 MGB