Remove the plug from the alternator and connect a test-lamp to the
brown/yellow. Its other side should be connected to ground. With the test
lamp connected like this both the test lamp bulb and the warning light
should be glowing at about half-brilliance (depending on the relative
wattages of the bulbs, the lower-wattage bulb will glow brighter).
If they are glowing then the fault is inside the alternator. If neither are
glowing then move the test-lamp to the warning light holder (bulb in place)
and try there on the brown/yellow then on the white (only the test-lamp
should glow here, at full brilliance). If it still doesn't glow than move
back towards the ignition switch on the white.
Remember that a voltmeter is quite capable of showing the presence of 12v on
a wire that has a high-resistance fault, whereas when you connect a
low-resistance load such as a bulb the 12v will vanish.
----- Original Message -----
From: Ciaccio Family <firstname.lastname@example.org>
To: MG Digest <email@example.com>
Sent: Monday, December 27, 1999 12:07 AM
Subject: Ignition Light Default
> Ok guys. The ignition warning light on my '76 B is not working. I have
> 12v to the light itself via the white wire. The brown/yellow wire goes
> back to the alternator negative side. I cleaned the contacts. Turn on
> the key and still the light does not come on (yes the bulb is ok). Any
> ideas out there?
> Dave Ciaccio