In a message dated 2/25/2002 11:56:13 AM Eastern Standard Time,
owner-6pack-digest@autox.team.net writes:
> On my 71 there are 3 white wires going to the fuse box. I can't figure out
> where the 3rd one goes and it is shorted to ground. I've traced one to the
> ignition switch, another to the coil as all the wiring diagrams show. No
> wiring diagram shows 3 white wires. I've poke around behind the dash and
> can't find any other destinations or find any damage to the harness. It
> looks like the 3 wire set up came from the factory since the harness
> doesn't
> look butchered and the unknown grounded white wire's insulation is molded
> to
> the wire it is on the same terminal with (to coil). Oh yes, it runs and all
> the electricals seems to function with the bad wire disconnected. I just
> don't like the idea of a grounded white (ignition) wire hanging around. Any
> ideas?
Russ,
The other white wire should go to the warning lamps for brake failure and low
oil pressure. With the engine off, the oil pressure switch is closed, so you
will get a low resistance reading to ground (through two lamps and the oil
pressure switch to ground, the lamps having a fairly low resistance). Try
measuring the resistance to ground with the engine running. You should get an
open circuit. If not, more looking is required.
The other option for this wire is to go to the ignition warning lamp. The
other side of the lamp goes to the field winding of the alternator, and it
too looks like a low resistance to ground when the engine isn't running. An
easy way to check for this is to look at the ignition warning lamp with the
key on but the engine not running. If this wire goes to the ignition lamp,
the the lamp will not be lit.
All of this is assuming you have disconnected this wire from the others to
make the test that showed a ground connection? If not, and the wire is still
connected to the other white wires, you will be reading the resistance of the
ignition coil which is about 3 0hms or less.
One of the kindest things you can do for yourself is to toss your continuity
tester in the back of a drawer that you never go into. I would say toss it
into the trash, but it may come in handy some day. Continuity tests can be
VERY misleading. You may think you are measuring the continuity of a single
wire, when in reality, you are measuring the continuity of a whole circuit.
Try this: remove the plug from the alternator, pull the white wire from the
coil, pull the white/black wire from the brake failure switch, and pull the
white/brown wire from the oil pressure switch, and check for continuity to
ground again. If you have continuity, you have a problem, but I'm betting
that you don't.
Dan Masters
Alcoa, Tennessee
Triumph TR 250 - TR6 Electrical Maintenance Handbook:
http://members.aol.com/danmas6/
Stuffing a V8 into a small British sports car:
http://members.aol.com/danmas/
British V8 Newsletter:
http://members.aol.com/danmas4/mgv8.htm
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