I've told this story in the past, but will repeat it as
we have gotten a lot more people in the last few years.
I was out on a TSD (Time Speed Distance) Rally, having a
grand ol' time driving about 70mph down a levy road
along the Sacramento River. Raised road, with various
bends to it, make a mistake here and you drop 20' into
a farmers field, or go for a swim.
Moon less night, around midnight, driving lights, heater,
radio (got to have some tunes), navigational lights, and
every electrical item was on.
Thought it was odd, as suddenly the floor was bright WHITE.
We could see our shoes, and every detail in the floor. Split
second later smoke started pouring out like crazy. Windows
down as black acid smoke filled the interior.
To top it off, everything went pitch black. Between the
white flash, and then pitch blackness... it was a little
tense coming to a stop, guided by lights on the river as
to guess which way the levy road was bending!
Thankfully we stayed dry, but the second thought entered
my mind... we were totally dark, sitting on a narrow road
with more cars approaching. I carried flares those days,
and got a few out to warn approaching vehicles. Whew.
A friend with a rope, towed us 30 miles back to a main
highway. At least we caught some sleep, and pondered the
extent of the damage. We had a long drive home, and no
wiring was left! The harness was one solid charred mess.
Alternator survived, regulator did not. So I used a dash
switch, that normally controlled driving lights, and wired
it up to the "F" (field) of the alternator. With an electric
fuel pump, and ignition coil, there would be a need for a
voltage source. Asked my navigator, Mike, if he knew how
a voltage regulator worked. "No idea". Explained he would by
the time we got home.
As the voltage dropped, I would have him play "regulator"
and turn on power to the field. Voltage would rise, then when
it got to 14.5V have him turn off the field power again. This
was usually a few times a minute. Five hours later he fully
understood what a regulator did.
Keep all this in mind, as I am very intense on the subject
of oversized alternators. I got caught off guard by a small
wire that melted, then melted more wires, then started a
pretty nasty fire. I had full "emergency" power switches
to kill all the power immediately.
MORAL:
Never assume "it never failed, so why should I worry" is
good enough.
Fusible Links: With 12 gauge wire, a 16 gauge fusible should
be used. Fusible links can be found at autostores. Nothing
but an undersized wire with a non-flammable insulation.
If you get a massive short, it will open, protecting the
harness. Cheap Insurance.
Connections: I love those "heat shrinkable molex connectors"
NAPA seems to be the only folks who carry them, at $8 package
for 5 connectors, seem like a waste of money. Hint, it is the
ONLY connector I'll use when repairing a harness. $8 is a lot
cheaper than walking when the power fails.
If you have a dead stock roadster: keep the alternator to 30
Amps (OEM sizing).
If you have lots of new electric loads (electric fan, driving
lights, BIG stereo, etc) then go with a larger internally regulated
alternator (50 Amp). Upgrade the wiring. Do NOT rely on the
stock wiring, nor ammeter.
With a 60 AMP alternator (hey, I had it sitting on the shelf),
I added THREE FUSIBLE LINKS: One off the alternator to the
stock harness. A second for the power lead off the starter
lug that goes to the fuse box. Third was a new lead from the
alternator directly to the battery.
If you add one of those "100 Amp jobs", run a 10 gauge wire
from the battery directly to the alternators "+" Terminal,
this should have a 14 gauge fusible link
.
Add a second fuse box (for all the new loads) from the Battery
"+" terminal. 16 gauge fusible link is good insurance.
Run an additional ground wire from the alternators case to
the "-" side of the battery (remember current always has
to return to the source, so think of the loop it flows
in).
16 gauge fusible links as I detailed above.
Oh, always carry a fire extinguisher. 10A:5BC (rated for
electrical fires).
Cheers,
Tom Walter
Austin, TX
email address: walter@roadster.sps.mot.com
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