Dear Spot,
Here are some ideas for you and Scott. Give
them a try and perhaps you'll get to complete
that ride!
> I have recently been edgycated in wiring 101
> thanks to Rick.
Thanks. It's all logical but everything seems
to be logical with 20/20 hindsight.
> But I can not figure out what the heck is wrong
> with my rear tail lights. ... The brake lights
> work, headlights work...I'm not sure about the
> rear turn signal.
Okay, let's start with what we know. The problem
is intermittant. That says that something is changing
and that usually means a loose or corroded connection
or a just-barely-attached wire. The problem is then
an 'open' circuit, not a short. A 'short' is really
a 'short circuit' and gets its name from the theory
that current will follow the path of least resistance.
That is the 'short' cut. An 'open circuit' means that
a connection is 'opening' or breaking contact.
On LBCs, open circuits are frequently caused by
bad, broken or corroded ground (earth) connections.
On plastic body cars like the Lotus Europa, that
problem runs rampant because all 'grounds' have to
be hard wired, not just wires attached to the body
where the negative battery lead is attached.
If the problem was a broken ground connection, it
would show up in all the rear lighting as they share
a 'common' ground ... the lighting fixtures. We now
then must move to the other side of the circuit.
> But this seems to happen all the time. I've cleaned
> the connectors, fuse box, giggled and wiggled wires
> too. It will sometimes just start working again and
> then stop. I know it sounds like a short...
...of course you now mean 'open circuit' now.
> ...some where. ...So I had to disappoint the dog...
This is of course, the real tragedy of this story.
>...and myself and head home. Any insight? Something
> I am missing?
You just need a methodical approach. You have the
tool you need.
> Is there a better method of tracking down the
> problem with a volt meter (which I have but don't
> have a clue how to use!)?
Okay, the voltmeter your reference is almost
certainly a volt-ohm meter and probably an ammeter
too. The trick is to make sure it is set properly for
the parameter you need to measure. The tool is robust
but can be damaged if set wrong, especially if it is
an analog meter with a gauge for display.
Here's what I suggest that you do.
+ Check the tail light assembly and verify the color
of the wire (insulation) for the tail light circuit.
While you are there, verify that all the wires are in
good shape, undamaged and the connections are firm.
We'll use that color-code later. (In British cars,
the parking light circuit is typically 'red' ...but
please double check.)
+ There are probably 'bullet' connectors there where
wires join. These are just metal tubes inside of
rubber slieves. Sometimes there are multiple metal
slieves inside, all connected together then covered
with the rubber insulators. THese are used to connect
multiple circuits to one source. Such is the way with
the tail light circuit. The tail lights, license
light and side markers will all be interconnected this
way.
The main body harness will supply current to the
lighting but only down one side of the car. The wires
typically connect at one tail light and go across the
rear valance inside the trunk, to the lights on the
other side. There will also be wires going to the rear
side markers.
+ Okay, time for a test. Turn on your parking lights
and verify that the FRONT parking lights are on. Your
front side markers should also be on. Now check the
rear. Are the tail lights on? If so, you are facing
the classic problem of intermittant electrical problems:
They work when you need them to fail so you can find
the fault! They fail when you need them to drive!
If the tail lights are NOT working, check the rear side
markers. Are they illuminated? If so, the problem has
to be back there in the trunk area as the sidemarkers
receive power from the same circuit as the tail light.
If the tail lights AND side markers are dead, the
implication is that no power is reaching the rear of
the car. However, the problem 'could' be just upstream
of the junction bullett. ... or could BE the bullett.
Check the license plate illumination lamps. Are they
on? All those lights are on the same circuit. I suspect
that in this case, they all die together implying that
the problem is forward of the trunk area. If SOME of
these lamps are working, you need to check connections
in the trunk. This is where the meter will come in
handy. If not, we need to verify that the whole system
is dead, just to be sure. Find that color-coded wire
again and trace it back to the last connector before the
harness going forward. Place your meter in VOLTS mode
and set the scale to something over 12 ... typically 20
or similar. Connect the black or negative test lead to
the chassis at a bare metal point. Try the point or
screw from the taillight assembly. Make sure that is
a good connecion. Push the tip of the positive,
typically red, meter lead into the wiring bullet so that
it touches the metal tube inside. What does the meter
read? If the circuit is truely dead, the meter will
read nothing or zero. If it reads 12V or similar, the
problem is in the trunk. If dead, we have to move up
to the interior area.
We should stop here. I gotta run. I hope this helps
you locate the problem. Total failures are always
easier to find than off-again, on-again problems. Yet,
you will find it!
> It is suppose to be 60 here today! TIA!
Yeeehaaa!
> Happy Holidays!
>
> Scott and Spot
Hey Spot, please tell Scott that I will be away from
the computer after noon. I will be traveling and bored.
My mobile number is 918-640-1492. Have him call and
we can chat our way through the next move!
Best regards, pats on the head, etc.,
Rick and Haggis in Tulsa
|