In a message dated 4/14/98 7:59:16 PM Eastern Daylight Time,
tomomalley@hey.net writes:
> Dan...are you saying that on a General Motors car a failure in oil
> pressure will illuminate the brake failure lamp?
No, just that they cut corners to save money too. An example of that is the
use of the brake lights for the hazard flasher on some of the '60s cars (they
may still do). The hazard flasher wouldn't work if you had your foot on the
brakes. Or Chrysler cars of the same era. If you accidently bumped the turn
signal lever while the hazard flasher was on, all the accessories in the car
that work only when the key is on would go on and off with the flashers.
> I can't trust the brake failure lamp...it's lying to
> me. :-)
No, it's not -- It's just not telling you what you want it too. When you
first turn on the key, it's telling you that the light bulb works. After the
engine starts, it's telling you that the brakes have failed if it comes on by
itself. If it comes on with the oil pressure light, it's telling you you have
low oil pressure. The burden is on you to know and understand what it's
telling you. I spent quite a few years designing control rooms for nuclear
power plants, and I can tell you I could not have gotten by with a design like
this. We could not place that kind of burden on the operators. Still, I
think it is a pretty clever design, given the cost constraints. How else
would you test a light from a switch that never operates in normal use without
tying it to some other switch, or adding complexity to the design -- time
delay relays, etc? Look at how MG handled it. They added a costly test
switch to the dash, and it still requires more participation from the operator
than the Triumph design.
> Holy Mackerel! No wonder you've been busy! I like the fuel level
> alarm. I take it the timer is there to buffer the set point?
A 555 timer is as close as you can get to a universal IC chip. It can be used
to do just about anything. I am using two of them in the fuel level warning
system -- one of them in a voltage comparator mode, and the other as a switch
to drive the lamp. The input has a very high impedance, so I can connect it
directly to the lead from the fuel sender to the gauge without impacting the
reading. Whenever the voltage on this lead exceeds a setpoint, the output of
the module goes high. The output will be fed into the other 555 timer, which
will turn on when the input is high, which can drive either a relay or a power
transister to turn on the lamp. I am using a PC board relay, simply because I
have one on hand. There is hysteresis built into both circuits, so I should
have no problem with the light flickering around the setpoint. If you get a
chance, you need to go to Radio Shack and pick up a booklet on this timer. It
is an amazing device!
> He he...part of me wants to modify the wiring of my Spit for better
> and/or more reliable operation. For example, if I ever refinish the
> dash again I'd like to add a second directional indicator. One for a
> left and right turn...just like a *real* car. Okay, OK...my car is
> really more like a VW and they only use one. :-)
I only used one lamp in my TR6/302, and it serves as the hazard flasher as
well. I was running out of room to place lamps.
>
> What holds me back though is my concern that I'll be creating a
> "custom" wiring job that is not documented in the manuals.
I have drawn my schematic on the computer, and I am making an "owners manual"
for the car, combining all the various inputs from the various venders used,
so I will have a ready reference later on when I have completely forgotten
what I did. I have a scanner, so I will copy all the pertinent photos,
diagrams, etc, that I might need in an emergency, and print them out into a
glove box sized booklet, along with the wiring diagrams, just like a factory
manual. The rest of the material I will gather into a folder, and keep in my
shop. Should my heirs decide to sell the car - I sure won't! -- then the
manual will go with it.
> I don't know how you feel, but whenever a Lister asks for help on an
> electrical problem, and then adds that he/she thinks the car may have
> been rewired, I get this cold chill up my spine. :-)
Amen! It makes it exceedingly difficult to trouble shoot via e-mail.
> Hey.....wait a second here. Did you decide to put that big ol' Ford
> lump in there just so you'd have an EXCUSE to add all the neat
> bells and whistles?
No, no! It's all about POWER!!!!!
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
'68 MGBGT---organ donor for the '74
|