[TR] TR3A Electrical Gremlins

Randall tr3driver at ca.rr.com
Sun Feb 1 09:34:05 MST 2009


> I am going to try 
> running a wire from the multi-ground post that is on the 
> instrument center dash to a good ground since this could be 
> the problem.

You should already have one.  The factory wiring included a wire from that
point to the 'E' terminal on the control box and another from the 'E'
terminal to the body nearby.

And the only thing powered from the ignition switch that relies on that
ground is the fuel gauge.  BTW, I would also suggest adding a ground wire
from the gauge to the tie point, if you don't have one already.  The ground
between the gauge & panel is dubious even with the PC.

> The brown/blue wire seems 
> to be about a 20 gauge wire

Should be MUCH heavier than that, approx 10 AWG.  Note that AWG (American
Wire Gauge) sizes run 'backwards', smaller numbers are larger wire.

> Any ideas on why this wire is getting so hot 
> and what I need to do to correct it?  

You have a short to ground somewhere.  The excess current through the short
is making the wire hot.  This is how cars catch fire ... and likely also
explains why nothing works.

One approach is to temporarily connect an old headlight bulb across the
switch terminals (with the switch off).  The short will make it light
brightly, but limit the current enough to hopefully avoid damaging the
wiring.  Then you can work at disconnecting various items (including wiring)
until the short goes away.

Or Mike's suggestion of a buzz box or powered test lamp is a good one, too.
Note that most digital multimeters include a "buzz box" function, but are so
sensitive that they will read continuity (and buzz) through even a small
lamp.  You can also work with an unpowered test lamp, like this one
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=4288
by using the car battery as a source.  Connect the lamp's ground to the hot
terminal of the battery, then look for wires that make the lamp light when
you touch them.  If the usual load is disconnected, then the wire must be
shorted to ground somewhere.

You DO have the 'green' fuse pulled at this point, right? 

Also, make sure you've got the right schematic for your car.  If you are
looking at a "TR3" schematic with no range qualifiers, it's probably wrong
in at least some details.  For 59, I think you should see the green wire
that runs out to the wiper motor and back to the brake light switch; plus
the in-line fuse for the tail light circuit.

Randall


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