Hi all...
On the "could they be stupid enough to run all that current thru a
voltmeter" thread...yes, they ran all that current thru an AMMETER. But
things changed a few years later, when they used an external shunt type
ammeter (really a voltmeter) on the trucks, as on the 1964 model that I
just worked on. With this setup, the meter just measures the voltage
drop across the big wire which connects the battery to the rest of the
truck wiring.
If you read the Ron Francis ads (he has been making wiring harnesses for
street rods for a long time), you'll see that others have the same
concern about sending all that current thru the dash wiring. Chr*sl*r
products used ammeters at full current up till sometime in the 70s, and
often had wierd problems when the ammeter stopped working...such as the
battery not charging, etc. The old Chevy ammeters are very reliable,
though.
In a perfect world, I replace the ammeter with an idiot light (connected
to the brown wire on the alternator). This allows me to run the red
underdash power feed wire straight out to the battery connection on the
starter, where I install a fusible link. These modifications make the
wiring more like newer GM cars/trucks, such as the 70s and 80s models.
The late late model GMs have gone to big fuses for everything, there are
2 big fuse panels on my wife's 99 Silverado! one underhood, one
underdash.
The solution? If you are using the truck in a normal way, with no power
robbing accessories such as killer stereos, A/C, funny lights, etc, then
you can use the stock wiring. Make sure the terminals at the ammeter
are tight, and that the nuts that hold the spades onto the ammeter are
tight. It'll work fine, I've been running my orange 59 this way for 25
years, with no wire smoke. It wouldn't hurt to add a fuse link (4 gage
numbers smaller [bigger number = smaller wire] than the main feed wire,
such as #16 link for the stock #12 feed wire) where the main power wire
connects to the battery cable.
If you are going to completely rewire the truck, using one of those
aftermarket harnesses, then replace the ammeter with a piece of red
translucent plastic, and put a light bulb behind it (some fabrication
required). The light connects to the brown wire on the alternator, and
the ignition switch wire. This lets you know when there's a problem,
and lets you run the power feed wire safely without worrying about the
voltage drop thru the ammeter and all that extra wiring. You can run a
properly sized feed wire (number 10) and a properly sized fuse link
(number 14), and all should be well.
THat's my take...please be careful with wiring, it can be dangerous!
Jim F
59s in AZ
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