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MG 1970s "Lighting Switch" - A Warning

To: mgs@autox.team.net
Subject: MG 1970s "Lighting Switch" - A Warning
From: jfischer@supercollider.com (James Fischer)
Date: Wed, 08 Nov 1995 10:23:29 -0500
I've been reading the list for a few weeks, and I'd thought I'd
contibute a small warning.

If you have the rectangular black rocker panel switches with the 
chromed plastic rectangular bezels around them, BEWARE!!

Look at a wiring diagram for your car.  

Note that >>ALL<< power to >>ALL<< lights goes through this single
switch. (At least on MG Midgets)

I was driving along the Blue Ridge Parkway on a recent cloudy night
(no starlight, no moonlight), and took a hairpin curve at about 45 MPH.

The headlights, running lights and all instrument lights went dead.

Lucky for me, I have both quartz foglamps and quartz driving lights, 
and the driving lights were on.  (Gotta see the deer to avoid picking
up a new 700 lb grille badge!)

The switch had simply worn out from years of use.  It had "jiggled" 
itself into being "off", when it was in the "ON" position.

It made me think - what if someone else had the same failure, and they
were picky about being "original" (no extra lights).  In this case, a
failure at the same location on this road could have been rather fatal,
or at least a good test of your rollbar.

What did I do?  I are an engineer, so I removed the Lucas switch, and
put three new switches where the Lucas one went.  They are pretty standard
little guys, and can be purchased from "Advance Auto Parts", among others.

They are colored rocker swiches, and snap into the same hole (horizontaly).
The three switches just fit into the space of the one Light switch (one
above the other).  The new switches also light up.

I have:
    Top     Yellow  (running lights)
    Middle  Blue    (headlights)
    Bottom  Red     (Fog Lamp relay)  This had been on a toggle switch
                                      that had been placed in the [silly]
                                      "fasten seat-belt" light hole on
                                      the center console.

My running light relay is still controlled by the "extra" switch built into
the washer/wiper lever (late 60s/early 70s Midget, and as I recall, MGA)

Now, if you let the "ground" for the indicator lights for these switches 
"float" (don't connect it to ground, but DO connect them together), what
happens is rather nice.  If ONE of the circuits is on, then the light for
that switch goes on.  Once you turn on the 2nd (and/or 3rd), all the 
indicator lights go out.  A cute little reminder that one has left 
something on.

I like the set-up so much, that I did the same thing over on the fan switch
side.  I now have a switch for the cockpit fan, a manual "override" switch 
for the electric radiator fan (required for mountain climbing in a Midget),
and an "extra" switch that I will use to control a relay to switch between
my primary electronic ignition, and my backup.  (I had one fail
once, and had to convert the car back over to points on the side of the
road due to the MGs "failure to proceed". -  MGs NEVER "break down", like
modern cars, they simply "fail to proceed".

Is it orginal?  NO.  
Is it good taste? NO.  
Must you cut into the original wires? NO.
Can you quickly convert back for a car show? YES.
Might it save your car and life? YES!!!!

If you want to stay authentic, then turn on your lights, and wiggle the
black surface of the switch with a finger.  Find out before you get killed.

As an aside, if you want to stay authentic, but want to add Fog/Running 
lamps, DO NOT run these devices without a relay with it's own power feed 
from the fuse box.  Getting your power feed from the "main" lighting 
circuit is not a good idea, since the lighting switch will NOT handle 
the additonal current drawn by current halogen accessory lights, on top 
of the headlights and running lights.  (This bit should be obvious, but 
I am talking about "lights" here...)

If you ever get a chance to drive the Blue Ridge Parkway, do it.  I live
along it, and I think it is the prettiest strip of road on the planet.
The large number of overlooks and pull-offs with parking and "easy-on,
easy-off exit/entrance lanes" make it a natural for a rally too.

It runs from Front Royal Virginia to Ashville, North Carolina (USA).
It runs parallel to Interstate 81, but is 15 miles east, and runs 
along the TOPS of the ridges of the Blue Ridge Mountains.  Most of it
it is "closed" to the general public after the first ice or snow.

Anyone who wants some switches and can't find them, e-mail me.  
I will be happy to mail them to anyone who covers the cost 
(about $3 US each) and postage. 

I might even draw up a wiring diagram, if asked.

The 2nd Law of Thermodynamics says "Natural processes increase entropy".
Translation  - "You think you're in trouble now?  Just you wait..."

   james fischer                       jfischer@supercollider.com



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