Russ,Dan
>From the wiring diagram for a 70-71 it looks as if the 3rd White wire
could be for a overdrive relay. White goes from fuse box to w1 on the
optional overdrive relay.
John Uloth
74 TR6
DANMAS@aol.com wrote:
>
> 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
>
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